OK, so your iPhone keeps restarting and you don't know what to do. Before you go further you need to know that there's a chance of being a software problem, usually an operating system issue (iOS), but there's also the possibility that the problem might be hardware related. If your iPhone is still opening you should definitely read on as this might be your last chance to backup your stuff.
In fact, there are two types of restarting that can happen to your iPhone.
- iPhone boots normally and after a while restart itself.
- iPhone don't get trough the boot screen and it keeps restarting. This is what is called a boot loop. Scroll down to step 5 if this is your issue.
If it is not a hardware related issue, the good news is that there are solutions for both cases and it can be easily done at home, so you don't need to go to a "specialist" that might charge you a ton of money for these operations. Let's get started.
Reasons for iPhone to restart
System issue: If this is happening after an update, you might had a corrupted file during the iOS download. Your internet might went down for a split of a second and a file might have been corrupted. To solve this we will be trying to reset the system.
Faulty Apps: Some apps may be just incompatible with your iOS version and it might cause the system to restart. To solve this, we will try to have a fresh copy of your Apps installed. Don't worry, we are not aiming for a one-by-one installation process.
1. First step. Backup your iPhone!
If you are in a lucky position where your iPhone boots into the system, connect your iPhone to the computer and create a backup using iTunes. If you will find out later that it's a hardware issue you'll be happy to have this backup and, even if it's not, we will be using this backup later in the process.
2. Update iOS and all your Apps.
It is easy to be done trough iOS Settings -> General -> Software Update for the system, and from the App Store simply go to Updates tab an click on Update all for the Apps.
If you are using a jailbroken device and the update part might not be the thing you want to do, than simply follow the next step, jailbreak your device again and install all your Apps and sources manually. Sorry, there isn't much else to to in this case.
TIP: You should not jump the the next steps after the updates. This may solve your iPhone 6 restarting problem so check your phone if it's restarting anymore. If the issue still persist, follow the next steps.
3. Reset iPhone Settings
Go to Settings -> General -> Reset and select "Erase All Content and Settings" to perform this action. I do hope you have a backup at this time because ALL your content will be erased at this point.
4. Restore your backup
Once you have performed the reset on your iPhone, you now can safely restore your stuff. Simply connect the iPhone to your computer and select to restore your latest backup. By this point, if you had a faulty App, the problem should be solved, as the App files are not backup up, but rather installed again from the App Store. This is how all your Apps will have a clean install with just a click of a button.
If for some reason, you had a really old App not compatible with your iOS version or not even available anymore in the App Store, that App will not be installed back. But don't worry, if the restarting was caused by an incompatible App, for sure that was the guilty one.
Now your iPhone should not have any restarting issues anymore. If that's the case, the following step is obsolete.
But if it still does, before concluding that it's a hardware issue, continue with the next step.
5. Perform a hard reset (DFU restore)
If you are here and your iPhone is still restarting or you're in a boot loop situation, the issue might be cause by the system itself and needs to be restored in DFU mode. If you don't know how to perform a DFU restore, we've made a tutorial for it here.
After the DFU restore is done, you can simply repeat step 4 to have your backup restored.
And now, if none of the above worked, you can really think about a hardware problem. If that's the case you should go to an iPhone service to have it checked out.