iPhone 18 Pro Keeps Restarting? 9 Real Fixes (iOS 27, 2026)

Jessica Graham

Updated on 2026-09-10 / iPhone Tips

An iPhone 18 keeps restarting for one of six reasons: an iOS 27 bug, an incomplete update, a conflicting app, battery/thermal stress, an inactivity security reboot, or --- rarely --- a hardware fault. Start with a force restart, then work through the checks below before trying an iOS repair tool or a full restore.

Watch one restart cycle first: does the Apple logo loop, does the phone shut off before the Lock Screen, or does it run fine for a few minutes first? That detail matches one of the six patterns below and points you straight to the right fix --- the same logic Apple's own troubleshooting flow uses, and the pattern that fixed the iPhone 16 Pro's random-restart bug via iOS 18.1 in late 2024.

Part 1: Why Does My iPhone 18 Keep Restarting, Rebooting, or Turning Off?
Part 2: How to Fix iPhone 18 Keeps Restarting After Update (Step-by-Step)
Part 3: How to Stop iPhone 18 From Restarting Again
Part 4: FAQs About iPhone 18 Keeps Restarting

Part 1. Why Does My iPhone 18 Keep Restarting, Rebooting, or Turning Off?

An iPhone 18 keeps restarting for one of six common reasons. Check what changed right before the problem started --- that narrows it down fast.

iOS 27 update bugs or an incomplete installation. If your iPhone 18 keeps restarting after iOS 27 update, the install itself may have failed or left damaged system files --- usually triggered by low storage, weak Wi-Fi, or an interrupted update. Apple recommends Recovery Mode when an iPhone can't update or restore normally.
A conflicting or outdated app. Your iPhone 18 keeps turning on and off if an app, widget, keyboard, VPN, or security tool hasn't been updated for iOS 27. Update your apps first; if the restart continues, remove whatever you installed or updated right before the problem started.
Battery health and thermal stress. If your iPhone 18 keeps rebooting during charging, gaming, or video recording, check whether it's overheating. iPhones use battery and performance management that can restart the device to protect internal components under extreme temperature or voltage.
A known launch-window software bug --- not unique to you. Recent iPhone generations have shipped with restart bugs Apple later fixed: the iPhone 16 Pro's random-restart issue (reported fall 2024) was resolved in iOS 18.1. If your iPhone 18 Pro / Pro Max keeps restarting on the very first iOS 27 build, an early-cycle bug is a real possibility --- not just something you did wrong.
Hardware defects in early-batch units (uncommon but real). A damaged battery, charging component, logic board issue, or liquid exposure can cause unexpected shutdowns. If your iPhone 18 Pro / Pro Max keeps restarting even after a clean iOS install, treat hardware as a real possibility and contact Apple Support instead of repeatedly reinstalling iOS.
Not every restart is a problem. iOS has an undocumented security feature --- confirmed by independent security researchers, not officially detailed by Apple --- that reboots an iPhone after about 3 days without being unlocked, to keep its data encrypted. A single restart after several days of inactivity is expected behavior, not a fault.

Quick Self-Check: Boot Loop, Random Restart, or Turning On and Off?

Use this table to confirm which situation am I in?

What you see	Likely situation	First action
Apple logo appears again and again	Boot loop	Force restart
Phone works for minutes, then restarts	Random restart	Check apps and battery
Phone turns on, shuts down, then starts again	Power/system problem	Charge and force restart
Problem started directly after iOS 27	Update problem	Update or repair iOS
Problem happens with one app	App conflict	Update or remove the app
Phone stays hot before restarting	Thermal/battery issue	Stop heavy use and check battery
Recovery screen appears	Recovery problem	Use computer-based recovery

This quick check matters because an iPhone 18 keeps restarting after update problem needs a different approach from a phone that restarts only when you open one specific application.

Part 2. How to Fix iPhone 18 Keeps Restarting After Update (Step-by-Step)

Work through these fixes in order. Start with the steps that do not erase your personal data. If your iPhone 18 keeps restarting after update, do not jump straight to a factory reset unless you have already tried safer options.

1. Force Restart and Re-Insert Your SIM Card

A force restart can clear a temporary system freeze without deleting your photos, messages, or apps. If your iPhone 18 keeps rebooting, this should be your first hardware-button test.

For an iPhone with Face ID, Apple recommends:

Quickly press and release Volume Up.
Quickly press and release Volume Down.
Press and hold the Side button.
Release the Side button when the Apple logo appears.

The Apple logo can take more than 10 seconds to appear. If the phone still does not start, Apple recommends charging it and trying again. If your iPhone 18 keeps turning on and off, you can also remove and reinsert a physical SIM card if your model and carrier setup use one. Turn the phone off first, remove the SIM, check it for visible damage, and insert it again.

2. One-Click Repair When Force Restart Doesn't Work

If your iPhone 18 keeps restarting after a force restart, an iOS system repair tool is the next step before a full restore. Tenorshare ReiBoot addresses this exact category of problem --- boot loops, Apple-logo freezes, and recovery-mode errors --- and supports iOS 27 through two repair modes: Standard Repair and Deep Repair.

Standard Repair is the safer option when your iPhone 18 keeps rebooting: it targets common iOS system problems without erasing user data. Deep Repair goes further for more serious system-level issues but can erase data, so back up the phone first whenever possible.

Download for Win

Download for Mac

BUY NOW

Key Features:

Standard Repair: Fixes many common iOS system problems, such as iPhone 18 battery draining fast, without deleting your personal data.
Deep Repair: Performs a deeper system repair for serious issues but may erase existing device data.
Boot Loop Repair: Helps address repeated restarts, including cases where the iPhone gets stuck on the Apple logo or iOS 27 is stuck on Update Requested.
iOS 27 Support: Covers iOS 27-related system problems and update issues, such as apps keeping crashing after the iOS 27 update.
Easy Repair Process: Connect your iPhone to a computer and follow the guided repair steps without complicated commands.

How to Use Tenorshare ReiBoot

Step 1: Download ReiBoot on your Windows PC or Mac. After installation, open the software and connect your iPhone 18 using a working USB cable.
Step 2: Once ReiBoot detects the device, click the Repair Operating System option from the main screen.
Step 3: Select Standard Repair to fix the iOS 27 stuck-on-Apple-logo or boot-loop issue without deleting your photos, apps, or personal data.
Step 4: ReiBoot will automatically detect the correct iOS firmware for your iPhone. Click Download and wait for the firmware package to finish downloading.
Step 5: Click Start Standard Repair and keep your iPhone connected during the process. ReiBoot will repair the damaged system files and fix the restart-loop problem safely.
Step 6: After the repair finishes, your iPhone will reboot normally. Once the Apple logo appears, the device should successfully exit DFU Mode.

This option is worth trying specifically when your iPhone 18 keeps restarting after iOS 27 update but hasn't shown any signs of physical damage or overheating --- that pattern usually points to damaged or unstable system files rather than hardware.

3. Check Battery Health

Battery and thermal stress explain a large share of iPhone 18 keeps restarting during heavy use cases. Check these four things in order:

Open Settings > Battery > Battery Health & Charging and look for unusual messages, reduced maximum capacity, or a peak-performance warning.
Note the battery percentage when the restart happens --- a restart that repeats near the same percentage points to a battery/power issue rather than software.
Watch for heat. If your iPhone 18 Pro / Pro Max keeps restarting while recording video, gaming, or charging, let it cool down before testing again.
Don't push through heat. According to Apple's iPhone battery and performance guidance, iPhones are designed to temporarily throttle performance or shut down when internal temperature exceeds a safe range --- this is expected protective behavior, not necessarily a defect on its own.

4. Find and Remove Apps Causing Crashes

If your iPhone 18 keeps rebooting after opening one particular application, update that app first. Open the App Store, check your account updates, and install every available update.

If the problem continues, delete the suspicious app and restart the phone. You can reinstall it later. Pay special attention to apps you installed immediately before the restart problem started. Also update widgets, VPN apps, keyboards, and other apps that interact closely with iOS.

5. Update or Reinstall iOS 27 Without Losing Data

If your iPhone 18 keeps restarting after iOS 27 update, a follow-up patch is often the fix --- Apple typically ships smaller point updates within weeks of a major release to address exactly this kind of bug.

First, check Settings > General > Software Update and install anything available.
If the update won't complete, connect the iPhone to a computer and use Recovery Mode.
Choose "Update," not "Restore," when prompted --- Update reinstalls iOS and tries to keep your data; Restore erases the iPhone completely.

6. Reset All Settings vs. Erase Everything

When an iPhone 18 keeps restarting but you can still open Settings, try the least destructive option first.

	Reset All Settings	Erase All Content and Settings
What it does	Resets system preferences (network, privacy, keyboard, etc.)	Full factory erase — removes all data
Your data	Kept	Deleted
Path	Settings > General > Transfer or Reset iPhone > Reset > Reset All Settings	Settings > General > Transfer or Reset iPhone > Erase All Content and Settings
Best for	A configuration conflict causing your iPhone 18 to keep turning on and off	A confirmed software-level fault, with a current backup in hand

Reset All Settings won't fix a hardware problem --- if restarts continue afterward, treat it as a hardware signal rather than repeating the reset.

7. DFU Mode and Full Restore (Last Resort)

Recovery Mode and DFU Mode are not the same thing, and mixing them up wastes time when your iPhone 18 Pro / Pro Max keeps restarting. Try Recovery Mode first; only move to DFU if Recovery Mode won't load.

Recovery Mode (try this first)

Connect the iPhone to a Mac or PC and open Finder (Mac) or Apple Devices/iTunes (Windows).
Quickly press and release Volume Up, then Volume Down.
Hold the Side button until you see the connect-to-computer screen --- not the Apple logo.
Choose Update to reinstall iOS while trying to keep your data. Choose Restore only if Update fails --- Restore erases everything.

DFU Mode (only if Recovery Mode fails to load)

Connect to a computer with Finder/iTunes open.
Quickly press and release Volume Up, then Volume Down.
Hold the Side button until the screen goes completely black (about 3--4 seconds) --- do not release yet.
While still holding Side, also hold Volume Down for 5 seconds.
Release Side only, and keep holding Volume Down for another 5--10 seconds.
Success looks like a fully black screen with no logo --- your computer should show a device-detected alert. If the Apple logo appears at any point, you held a button too long; start over.

DFU is a firmware-level restore and normally erases the device, so back up first whenever the phone allows it. Treat both modes as a last resort after updates, app checks, and system repair haven't worked.

Part 3. How to Stop iPhone 18 From Restarting Again

Fixing the immediate issue is only half the job. These simple habits can reduce the chance that your iPhone 18 keeps restarting again after the next update.

Prevention Checklist for Every iOS Update

Before installing a major iOS update, keep at least one current backup. Make sure your iPhone has enough free storage and charge the battery before starting. After updating, give the phone time to complete background tasks. Then update your apps from the App Store. If your iPhone 18 keeps rebooting after an update, do not install several unknown apps at the same time. That makes it harder to identify the cause.

Use this short checklist:

Back up your iPhone before major updates.
Keep enough free storage available.
Install updates over a stable Wi-Fi connection.
Update important apps after iOS updates.
Avoid heavy gaming while an update finishes.
Watch for unusual heat or battery behavior.
Remove apps that repeatedly crash.
Keep your computer available for Recovery Mode if needed.

When to Contact Apple Support

Contact Apple if your iPhone 18 Pro / Pro Max keeps restarting after you have completed software troubleshooting, especially if the phone gets very hot, shows physical damage, cannot charge correctly, or restarts even after a clean restore.

Apple also recommends service when you cannot update or restore an iPhone through Recovery Mode or when a required button does not work.

If the device is new and the problem appeared without any clear software cause, keep your purchase information and repair records ready. A repeated hardware fault should receive professional inspection instead of repeated software restores.

Part 4. FAQs About iPhone 18 Keeps Restarting

1. Why does my iPhone keep restarting on its own over and over again?

An iPhone 18 keeps restarting because of software bugs, an incomplete iOS installation, faulty apps, battery problems, overheating, or hardware faults. Start with a force restart and app updates.

2. How do I fix my iPhone from restarting loop?

If your iPhone 18 keeps restarting after update, force restart it first. If that fails, check battery health, remove suspicious apps, update iOS, and try ReiBoot Standard Repair before a full restore.

3. Can a bad battery cause a boot loop on an iPhone?

Yes. A battery or power problem can cause unexpected shutdowns and repeated restarts. If your iPhone 18 keeps rebooting during heavy use or at a certain battery level, check Battery Health and seek service if needed.

4. How to use Recovery Mode to fix a restart loop?

If your iPhone 18 keeps turning on and off, connect it to a computer, enter Recovery Mode with the Volume Up, Volume Down, and Side button sequence, then choose Update first. Apple says Restore erases your data.

Conclusion

An iPhone 18 keeps restarting problem does not always mean that your phone has a serious hardware defect. Start with a force restart, check the battery, update or remove problem apps, and install the latest iOS version. If your iPhone 18 keeps restarting after iOS 27 update, use Recovery Mode or an iOS system repair option before moving to a complete restore.

If your iPhone 18 Pro / Pro Max keeps restarting because of damaged system files, Tenorshare ReiBoot can provide another repair option. Its Standard Repair mode is designed to fix many iOS system problems without deleting personal data, while deeper repair options require more care.

The safest approach is simple: start with the least destructive fix, protect your backup, and move to a full restore or Apple service only when the easier solutions fail.