My PC Restarts While Trying to Game (My Problem seems to be unique)

Dec 2, 2018
My issue is, while playing games on my PC, it restarts on me, or the game will crash and I'll be at the desktop. It has been doing this the past week mainly on Fortnite, and I've put up with it because I'll have a new PC around Christmas. I've been playing Fortnite on this PC for around 6 months and have had no problems until now. At epic Graphic I get 50 Fps and then close to 120 at low. I've checked my drivers and updated everything I could, but I'm not sure that was the problem. Another thing is it seems to have progressively gotten worse, just yesterday I'd be in a match and it would crash mid game, but now it crashes just loading into the lobby. I've wondered if it was an overheating issue, but its hard to test when I can't get in a match. I have checked to see if my hard drive is fragmented, it wasn't, however when booting my computer it says along the lines 'Scanning and repairing drive C:' and what I believe to be the label of my drive. What are do you suggest I should do? As well as ways of troubleshooting?
My specs are the following.
- Processor AMD Phenom(tm) II X6 1090t Processor 3.20 GHz
- 8 GB of Ram
- Windows 10 Pro
- 650 Watt Power Supply
- Ge-force 750 Ti Graphics Card
- 2TB Seagate Hybrid HDD (Contains my Version of Windows)
-1TB WD Blue HDD
Update : 1
I've replaced the thermal paste on both my GPU and CPU, and thoroughly cleaned my fans. Yet I still have the same problems. I'm thinking it might be a problem with my hard drive because I've already updated all my drivers, and have noticed very high usage on my drive, even without much going on.
Update : 2

I've ran a diagnostic on my hard drive and windows found no problems. When I launch a game it either gets to the loading screen, or the lobby, then instead of a blue screen of death, The resolution seems to pop up showing '1920 by 1080p Aspect Ratio' (etc) and the audio glitches, then the computer restarts. Once again I've checked my display adapters for new drivers, and checked for updates but everything seems to be up to date.