1| You forgot to include the make and model of your motherboard as well as the OS you're on. Please include them.
2| Does this issue crop up only when you game? If so which games have you tried on your system to repeat the issue?
3| Have you made sure your motherboard BIOS as well as your GPU drivers are up to date?
4| From the looks of things it reads out like your PSU is failing. How old is it?