My phone has been restarting itself nonstop for the past hour and a half. It did this yesterday and I drove the the store, once I got to the parking lot of the store my phone was fine and the second I got back into my house, it did the same thing again. Even if I take out the battery, the second I put it back in, it starts restarting itself over and over again.
Try the instructions to place your device into Safe Mode.
If the issue quits, then I would start deleting apps atarting with the newest downloaded to see if an app or an app conflict is causing it.
If that does not fix the issue, then try removing the SD Card and power up the device and see if that corrects the issue.
If that does not work you may have to do the dreaded Hard Reset
Be sure to save any pix and documents and backup your contacts prior to doing the hard reset.