Computer Acting Choppy And Sluggish After Closing Games

As of maybe a month or two ago my computer has been acting rather strange. The first thing I noticed is that now whenever I need to restart my computer (for updates, ect.) the screen will flash for a few seconds, return to normal, flash for another second or two, and then properly restart. Then a few weeks after that, I noticed my computer having trouble when I play games on my comp (I built my comp originally as a gaming rig).

After exiting games like Minecraft, Red Orchestra 2, Total War, or any of the other games I play, my computer will act sluggish for a few minutes after they close. It generally takes a minute or two until my comp seems to be back up to speed. Another thing is that my computer seems to have a difficult time closing my games, especially Red Orchestra 2. When I exit RO2 my comp will sit there at the game screen as if its frozen (I can't move my mouse or anything) and then finally exit the game.

Then, after exiting the game my comp screen will be all distorted and it will take another 10 seconds or so for the screen to return to normal. RO2 is definitely the worst when it comes to closing, all of the other games for the most part close fine, but my comp will still perform slowly after I exit any game. Normally, after I exited a game I could jump right in to my browser, start menu, or any other app if I wanted to.