So my CPU was running in the high 80's maybe cause its getting old im not sure. So I bought a aftermarket cpu cooler. noctua nh-u125, which works amazing. Im down to 45c under load. Anyrate I installed as per instructions which involves tightening the cooler down to the mount. Well long story short I over tightened the screws which was putting too much pressure on my cpu and was causing my pc to go into a turn on for 5 seconds shut off and back on loop. After lots of trouble shooting I sat back and thought to myself what has changed to cause this. Duh the cooler is the only thing that is new to the system. so I took it off and reinstalled it, but just snugged the screws. Problem solved! no more start and restart loop. Just wanted to add this to the possible solutions to "Why is my pc turning off and on?"