Welcome to the forums my friend.
We would require much more information than this such as:
- Your full system spec including PSU make and model (not just wattage and brand)
- Specifically what actually happens, does it shut off as if you unplugged it suddenly from the wall?
- Have you changed anything recently? When has the problem started occurring?
- Does the problem only occur in certain situations, such as gaming etc.
- Do you have latest drivers and BIOS installed?
- Are you running any overclocking or XMP?