As a fun problem analysis exercise....it only started happening with the new Video card install.
So you've possibly (1) upset your cooler seat,...that is the stock cooler is not doing its job that it was doing prier to the upgrade ooooooooooor!,(2) that new vid of yours is generating a lot of heat that was not present before!!! case temp went through the roof ... calling for cooling.
The fix before going out to spend more money......Thermal paste and R&R CPU-Cooler, then run...did it fix it ???.........next, ... side off case and run again,...if temps are closer to normal, spend less money on a couple of extra case fans
Aussie Allan