Hi Joe,

This sounds like a overheating or possibly hardware related issue.

When your computer hardware  (CPU, GPU etc.) overheats, it can affect the way your computer behaves and cause it to lock up and shutdown in extreme cases.  The easiest solution is to open up your PC case (tower), clean out the insides with a can of compressed air, check all cables/connections and power your PC back on to see if it helps. Make sure your case fans are working too. You can use an app like HWMonitor or CPUTemp to monitor system temperatures.

The other possibility is your graphics card acting up. A flaky graphics (video) card can result in a fuzzy screen and cause system freezes. You will need to try booting up your computer without the graphics card to see if that helps. It could also be your computer's onboard graphics chipset that is failing, in which case you will need to get it checked and replace the entire motherboard.

Running resource intensive apps or installing buggy drivers (esp. video) are also known to cause such problems.

You might need to take it to a repair shop if all else fails.

Good luck,

James