Windows 10 suddenly started lagging at programs and games!

Oct 1, 2018
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Windows 10 suddenly started lagging at programs and games!
Everything was running smoothly on my new PC, until 2 or 3 weeks ago everything changed:/
GPU driver is updated ( windows too), and it still lags in games and programs… I’ve seen all the posts before about windows lagging, but I still can’t find the right answer for my case...

Please help!

i7-8700k
GTX 1080Ti
Asrock z370 extreme4
Nvme Samsung ssd 960
32G ram
Direct X 12