Question Fullscreen apps stuttering, feeling like 20 fps

[Domce53]

Hello,
I've recently noticed, that when I play games or open anything in fullscreen, sometimes it stutters like crazy and is really frustrating. I'm using a 144hz monitor, and I can clearly see when it starts. The mouse and the whole screen is laggy, but when I hit ESC to open the game HUD or ALT+Tab to other apps, it just fixes. I've tried to update, reinstall the graphics card drivers, updated all drivers and windows, but nothing helps. The nvidia geForce shows me that I have ~170FPS but it feels like 20.

 

[rgd1101]

full system spec?

 

[Domce53]

full system spec?

CPU: I5-9600k oveclocked to 4.6Ghz
GPU: ROG 1060 6gb
MB: Gigabyte Z390 gaming x
16 GB DDR4 ram 3000 mhz
1TB Crucial M.2
650W PSU

I don't really think its the systems fault, because when I restart the PC and launch the game everything is good, but if I use it for a couple of hours and then launch something, it starts stuttering.