I had the same problem, once I tap the power button my phone restarted again and again. I found the following self discovered method the most easiest and riskless one: Just tap the power button repeatedly while the OS is in reboot mode and carry on tapping the button until your OS is ready. OS may restart again or it may not. You might not be successful in one or two attempts. The phone might restart again and again. Continue doing so until your phone restart problem is resolved. Important note: The frequency of tapping of power button should be fast. It must be tapped quickly or this method will not work.