Question PC stutters, increasing in intensity with use ?

Apr 6, 2020
Hello people , I have been trying to troubleshoot the problem in my system for 2 years with no success.
My specs:

Z390 Gaming Plus (previously ROG Z270, swapped because it had 3 bent pins in CPU socket which was NOT the source of the problem)
8x4 Corsair Vengance 3000 mhz CL15 RAM(2 of 4 sticks are new to test out if it was the RAM causing the problem)
Strix 1070
Samsung m2 960 and 970 nvme
Temperatures are cool never going past 60 and the CPU is overcloked to its Turbo and XMP enabled.

Some patterns I've noticed:

When I first power the system after a night it runs buttery smooth for about an hour or two. Then, gradually starts to stutter 5 fps for 0.3 seconds then 10 fps for 1 up to 200 fps for 2 seconds maybe even more if I keep using it. Restarting PC alleviates to a point but it doesnt go back to its first boot state.

I've ruled out the problem being GPU because the stutters happen even in Microsoft Word after use and even when I am typing this.

The most I used my CPU is around 90% when I run 1 game on the background and play 2 others. Which doesnt seem to have any relation to the stuttering. Utilization spikes about %10 - %15 when the stutters do happen so there is that.

Cores and threads are recognized and Memtests and other diagnostics I have used came with 100% success.

I can't test my system with another CPU and to be honest it is the only part I haven't replaced yet other than the GPU.

I am looking for additional diagnostics I can use to determine the root of the problem and try to change my CPU if there is no saving it.