Games crashing

Hi All,

My pc is frequently crashing while playing games and I am trying to narrow down the cause.

Crashes will happen anywhere between 10 minutes to -4 hours of gaming randomly.  Not seeing any BSOD.  Pc just crashes and stays stuck on the last frame.  Only option is to switch off with power button.

cpu and gpu are both typically averaging 65-70C while gaming.  

windows event log shows pretty much nothing at the time of the crashes.  Only an error about power kernel 41 after I switch the pc back on. 

any idea where to start looking?