Computer Randomly shuts off, but hardware is this running

My Problem
Hi, I've been using a custom built gaming computer for the past year or so and have encountered no problems until now. Recently I will get this issue where while I am gaming, idle, or just browsing the web my monitor, keyboard, and mouse will shut off. All my fans lights and what not are still running on my computer. The only way to turn the computer off is with the power button. Also, sometimes to computer will not reboot right away and will take 5-30 before working again.
What I've tried
1-
I checked all my cords made sure nothing wasnt plugged in.
2- I clean my computer often with compressed air so dust isnt a problem.
3- I checked my RAM, its fine.
4- All my drivers should be up to date.
5- I don't think its a over heating issue, I have pleantly of fans, and because of this I put my CPU speed down to 2.9 ghz instead of 3.5
6-Checked the GPU's fans, plug ins, and drivers and everything is fine.

My Computer Specs
CPU:
AMD FX-8320
GPU: Radeon HD 8750
PSU: Corsair CX600
Motherboard: Asus M5A78L-MLX Plus
RAM:Corsair Vengance 8GB 2x4
HardDrive: Barracuda 2TB
 
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