Computer shuts down after some minutes

[Nice]

do you smoke or have any house pets such as cats running around your computer? If so, i'd very much suggest that you thoroughly examine your fan if there's any cat fur in there or if you smoke in the presence of your computer there's a fair chance that there's a thick layer of (i dont know how it's called in english, its a yellowish thing) and its bad for your fan.

Other than that and the "clean your computer" i have no idea what might be causing this. My GPU used to be at 85°C when idle and around 100°C when playing games (in which case my computer BSOD'd a lot) and the only thing i did was i cleaned the fan and now it runs at 60°C on idle and 80°C when playing games.