Never had this issue untill it automaticly updated to the newest os (jelly bean?). The night it updated and installed right after the installation it kept restarting every few seconds. I booted in safe mode and it made no difference. I have few apps installed anyways so I doubt there's any conflict.
I left it off over night and the next day it was back to normal. However twice since the update for seemingly no reason it will shut itself down, then restart, and continue restarting every 30 seconds or so.
Is this a known issue? It never happened when the phone was running off ICS, only after it updated.