Need Help With Random Restarts

[Wilsyn]

Have had my tower for roughly 2 years and this week I got a couple of freezes/only froze for a couple minutes followed by permanent freezes only solvable by restart and now my computer is randomly restarting anywhere from 30 minutes to several hours into running.So far I've opened it up and cleaned it out trying to reduce the chance that it could be overheating, ran Memtest (no problems), and am currently looking through GPU-Z to find anything out of the ordinary but am stumped. The only 2 things I think it could be would be my Graphics card (Nvidia GeForce GTX 660 ti) or my power supply unit (Corsair GS800). If anyone's had a similar issue or knows of anything that I haven't checked yet would love to hear some feedback. http://i.imgur.com/7PZ7Xwd.gif
http://i.imgur.com/Rl8G7r9.gif

 

[Quaddro]

let's examine the symptom.

freeze and restarting is an indication that your system is lack of power, and/or overheating..

so let's try this.

1. reapply thermal paste to your processor.
2. make sure that your psu cable connector to your motherboard is tight.