Well, first thing – don’t panic. At any given point, at least two or three people crop up having the exact problem. Quite a number of people – thousands, in fact – have this problem where the iPhone keeps rebooting after jailbreaking, or after iOS downgrading or even simply after replacing the battery. Sometimes it happens when the iPhone has fallen and experienced a shock of some sort accidentally.
Most of the reasons include jailbreaking, iOS downgrading, accidental falls and impacts, software downloads or upgrades and battery replacement. If your iPhone keeps rebooting after iOS downgrading or the iPhone keeps rebooting after jailbreaking, it most certainly cannot be easily rectified because you can do something only when the iPhone starts up right?
Of all the methods prescribed, the DFU Restore method seems to be the standard working method which is worth trying because it has the maximum chance of working. The DFU Restore – if you haven’t heard – is a complete restore. You’ll lose your jailbreaking data – in case you have jailbroken your iPhone. If you have a carrier unlock and other such jailbreaks done to your iPhone, you’ll lose all that data because we are going to do a complete restore of the iPhone.
Of course, you can re-unlock and re-jailbreak your iPhone once you have completed the restore. As in most cases, there is no guarantee with the method. All we know is, quite a lot of people who came up with the “iPhone keeps rebooting” problem have found solace and solution by using this method.
Attention: You may lost your data while doing this process. So it would be better to have back up of your data.
The DFU Reboot:
Connect the iPhone to your computer
Shut down the iPhone
Now, hold the Power and Home buttons simultaneously.
After about 10 seconds, release the Power button, but keep the Home button pressed.
An iTunes popup saying “iTunes has deteceted an iPhone in recovery mode” will appear.
Now you can release the Home button. A blackout screen appears – this is the DFU mode. A recovery will be attempted.
If a successful recovery is made, your iPhone will be completely recovered.
In all probability, the iPhone will no longer keep rebooting. In case it is a problem arising out of issues like replaced battery or an accidental fall causing internal damage, you’ll need to get it replaced as it might be a hardware-related problem.