If it is due to CPU overheating, maybe can replace the thermal paste..
Thermal paste is the stuff that goes between the heatsink and the CPU. It is supposed to enhance the transfer of heat from CPU to the heatsink, so that the heat can be dissipated. I guess it is possible that the thermal paste might need replacement..
Search for and download this utilty known as OCCT. If you run it, it might help diagnose the problem - temperature, PSU stability