Overheating with new thermal paste

Daytona Beach

Prominent
Aug 3, 2017
19
1
525
So my computer didn't want to let me install Windows 10 with my new CPU for some stupid reason so I put my old one back in to install 10 and then put my new CPU in and it didn't start. So I placed my old CPU back in and reverted to 7. Then reinstalled my new CPU, anyways, now the computer randomly shuts off when I start one of my games. It'll run for about a minute then shut off, no warning message when it restarts such as "PC shut down due to CPU overheating". Nothing, starts up like nothing happened. All but 2 of my PC parts are new and have been working just fine for almost a month now so its not the PSU going out or anything like that. All wires are plugged in, all fans are working, there's 4 in my case if you include the PSU fan and GPU fan. Only stock parts are the motherboard and RAM. It was running at 50-55 degrees Celsius before I took it out, running RBS Siege on max, now it runs 75-80 degrees Celsius while running Cinebench. Any ideas why? Yes the right amount of paste is on the CPU and the CPU fan is mounted properly. I made sure of it and I always put the same amount on the CPU. (I used the dot method)

EDIT: Ran Cinebench again, came out with 305cb, CPU heated to 78c max but came back down to 50c after the test was done. I do not know what my CPU was running while playing games before I took it out.