Go to control panel, then hardware and sound, then to the power plan and set it to high perfomance, second might be 12V rails.
Which PSU is in question?
Second option that i would try is to clean the drivers completley, download DDU (display driver uninstaller) go to safe mode ,
here windows 10 guide to safe mode;
https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10 use SHIFT+RESTART method.
After unpacking and launching DDU run Clean and restart, after restarting download latest drivers and install them.
Now have you tested that scenario in games? Or just into Furmark?
And also try koleto's advices.