It's possible. In my opinion, 50°C is oddly low for your computer to shutdown on. The mobo has the thermal sensors, and if one of them is bad, it could be only reporting 50°C, but in reality, your temp could be higher. Still, even that is a stretch, because to reach a thermal shutdown temp, you'd have to be doing some serious OC w/o aftermarket cooling.
Where are you reading the temp at, the Hardware Monitor just before the OS loads?