Bunraku

Hi Had my PC for a few years and had no issues. About 2 months ago i changed from Nvidia GTX 970 to RTX 2070. Not sure if cause as first month was great, but last month my PC has been having 3 kinds of problems. BSOD with Stop Code Errors. stop code kernel security check failure PC just freezing. CTRL-ALT-DEL having no effect and having to hold power button to reboot PC. I have run CHKDSK Sfc /Scannow Uninstalled Anti Virus Verified Drivers I have no hardware attached to PC apart Keyboard and Headset Reinstalled Windows and now don’t seem to get BSOD. However still get PC freezing when playing Call of Duty and GPU temp was 71° at moment of freezing and i had only turn PC on a few minutes before and the temps usually go higher no issue. I’ve also since played it for 3 hours since with no freezing. Using Powerdirector for video editing my PC froze and again only turning power off fixes it. And just Random Shutdown yesterday trying new Total War Try yesterday. PC just shutdown. Fans still turning, but black screen. Had to turn off at power to restart. Any ideas whats the issue? Thanks