I haven't overclocked anything.
CPU temps at idle ~30° under load ~40-47°
GPU temps at idle ~25° under load ~70°
This basically only occurs while playing games. Everytime I play the crew and switch into the 3d rendered world it takes 10-60 seconds for the PC to shut down. Today I tried to play Bioshock Infinite at completly maxed out settings, which put the load to 99% and everything went well for roughly 15 minutes until the screen went black and the PC rebooted. CSGO runs mostly fine, but in some competetive matches this happens every 10 minutes. Basically completely random.
I have even added 3 extra fans to my system to prevent better airflow, which didn't really change anything from what I noticed.
Also it is most likely not am os failure, since I recently switched from Windows 8.1 to Windows 7 and the error persisted.
Specs:
CPUIntel Core i5 4670K
MotherboardMSI Z87-G45
RAMCorsair Vengance 1600Mhz 16GB
GPUZotac GTX 780 AMP
CaseNZXT Phantom 530
StorageSamsung 840 Evo 250GB, Seagate Barracuda 2TB
PSUCorsair CX750M
CoolingCorsair H100i