If your iPhone is restarting randomly, while charging or stuck in a restart loop, you will find below the steps to Fix iPhone keeps Restarting problem.
iPhone Keeps Restarting
While the problem of iPhone Restarting has mostly been reported by owners of old devices, this problem can occur on any iPhone, including new devices.
The reason for iPhone Restarting can range from minor software glitches, malfunctioning apps and corrupted software to hardware related problems.
In terms of severity, this problem can range from iPhone Restarting once in a while or only while charging to iPhone being stuck on a Restart Loop.
A. iPhone Keeps Restarting While Charging
In this case you have an iPhone that works well, but keeps turning ON and OFF while charging or whenever it is connected to a headphone.
This problem is mostly related to faulty charging cable, debris or lint stuck in the charging port or a faulty charging port.
1. Clean Charging Port and Headphone Jack
Use a toothpick to clean the charging port and the headphone jack on your iPhone.
Make sure that you take all the care and precautions to avoid damaging the charging port and the headphone jack.
2. Change Lighting Cable:
Inspect the charging cable to see if is damaged or broken. If it looks alright, it is possible that it has become faulty.
Hence, try charging your iPhone with a new or another charging cable and see if this fixes the problem on your iPhone.
B. iPhone Stuck in Restart Loop or Restarting Randomly
While the problem of iPhone Restarting once in a while or being stuck on a Restart Loop is mostly due to corrupted or incompatible software, it can also be due to hardware related issues.
1. Force Restart iPhone
You might be able to get an iPhone out of the Restart Loop by force restarting your device.
iPhone 6 and below: Press and hold Home + Power (ON/OFF) buttons, until you see your iPhone starting with Apple logo.
iPhone 7/7 Plus: Press and hold Volume Down + Power (ON/OFF) buttons, until you see Apple logo
iPhone 8 and above: Press and release Volume Up > Volume Down > and then press and hold the Side button (ON/OFF), until Apple logo appears.
2. Check the SIM Card on Your iPhone
If your iPhone appears to be stuck on a restart loop, the problem could be due to a faulty SIM card.
An easy way to rule out this cause is to simply remove the SIM Card from your device and see if the problem disappears.
1. Shut down your iPhone and remove the SIM Card from your device by using the SIM Ejector tool or a paper clip.
2. After removing the SIM Card, Restart iPhone to see if the problem is gone.
3. Put the SIM Card back into iPhone and see if the problem comes back.
If the problem comes back after replacing the SIM Card, it points to the SIM Card on your iPhone being damaged or defective.
You should be able to fix this problem by replacing the defective SIM Card with a New one.
3. Backup iPhone
Before going ahead with the next steps, it is a good idea to secure the data on your device by making a backup of your iPhone.
If your iPhone is accessible, you can go for a manual iCloud Backup and also make a complete backup of your iPhone on Windows computer or Mac.
If you are not able to access your iPhone, you will have to go for a Recovery or DFU Mode Restore (See method #8 below)
4. Check for iOS Update
It is quite possible that the iOS operating system on your iPhone is not being automatically updated, leading to the Restarting problem.
1. Go to Settings > General > tap on Software Update.
2. On the next screen, allow iPhone to check for updates and tap on Download and Install link (If an Update is available).
After installing the update, restart your device to see if the problem is now fixed.
5. Update Apps
Similarly, the Restarting problem can also be caused by Apps on your device being outdated.
1. Open the App Store on your iPhone > tap on Updates tab, located in bottom menu.
2. On the next screen, tap on Update All option or update only the required Apps by tapping on the update option located next to the Apps.
6. Reset All Settings
Sometimes the problem can be caused by incorrect or corrupted settings on your device.
This can be fixed by Resetting only the Settings on your device to Factory Default Settings. In case you are concerned, this step does not erase any data on your iPhone.
Make sure that you note down the WiFi password on your iPhone and follow the steps below to Factory Reset All Settings on your iPhone.
1. Go to Settings > General > scroll all the way down and tap on Reset.
2. On the Reset screen, tap on Reset All Settings option.
3. On the confirmation pop-up, tap on Reset All Settings to confirm.
After the Reset Process is completed, join the WiFi network and see if your device is now working fine.
7. Restore iPhone Using Stable Backup
If you have a recent stable backup of iPhone stored on your computer, you might be able to fix the problem by Restoring your device using the stable backup of iPhone.
You can find the steps to Restore iPhone using Backup in these guides: Restore iPhone From Backup on Mac or Restore iPhone From Backup on Windows Computer.
8. Restore iPhone Using Recovery and DFU Mode
If a regular Restore is not helping, you can go for Recovery and DFU mode Restore to fix this problem on your device.
Recovery Mode Restore erases all the Data on your device, reinstalls iOS operating system and provides you with the option to Setup your device as New iPhone or Restore using Backup.
DFU Mode Restore also Erases your device, reinstalls iOS operating, reinstalls device firmware and provides you with the option to Setup your device as New iPhone or Restore Using Backup.
Unless your device has a hardware related issue, any of the above methods should help you fix the problem on your device.
9. Replace The Battery
On older iPhones, the problem of iPhone restarting randomly is being attributed to its battery.
If you have tried all the above steps, the last option is to take your iPhone to Apple Care and ask them to take a look at your device.
Apple Care may either advise you to replace the battery or come up with some hardware issue.