Toshiba laptop shutdown and keeps restarting

[Scarlet2015]

My laptop Toshiba shuts down and then it keeps restarting, until I perform a hard reset (unplug, take out battery and press power button for 2 minutes), then it works but only for a few minutes, max 2 hours, after that the problem repeats itself, HDD and RAM tested 100% health
P.D. It isn’t an overheat problem, all tests already done.
Toshiba Satellite P755, core i3, 4Gb Ram

 

[zer0c007]

See this thread;
http/www.tomsguide.com/answers/id-2371004/toshiba-satellite-shuts-sec.html