If it was the power supply, you'd be seeing nothing.
When the computer starts up, look for "Esc"
Delete" or an f value of f2 or f10. You must hit that button to get to the BIOS setup.
If it was the processor it would be due to overclocking or the thermal paste being worn out.
If it was the motherboard, it wouldn't even turn on.
Go and see if you can access the BIOS.