if its not hardware related issue then it could be a virus of some some that runs at startup to set your pc to restart in an infinite loop.
what you can try is booting up in safe mode and see if the same thing happens or you can boot normally and hold the shift key while its loading to windows. this will prevent any tasks that start up on boot. from there you can check your startup tasks to monitor if any program is running that shouldn't be on there. i would also suggest you run checks for viruses spy/malware etc