I need some advice

My system seems to be shutting down on and off, and getting pretty regular about it. I can be working on something or play a small base game and bam! Restart, So I took off the side panels and removed everything and cleaned it thoroughly. But this did not help. So I looked into my setting and seen all my setting are as they should be, I think! Well the system is still going into a restart. Can someone help me with this one please, Thank you