Weird lag spikes out of nowhere

[Danielkuhr35]

Hello everyone, i seem to have a problem that no one has ever posted about, or at least not for the good 5-6 months i've tried to resolve this problem.

The game i will be showcasing and using examlpes from is LMU (Le Mans Ultimate). https://streamable.com/egcepq
https://streamable.com/z6ww1x 
My computer can run it just fine and atm i run it at med/high setting, with about 80-90% load on GPU and 40% CPU, i run at 60fps due to my old humble moniter only being that.

But then suddenly, seemingly out of nowhere i get lag for around 0,5 sec and then again after 5-30 seconds i get one that's usually a bit longer than the first, i have attached a clip where it can be seen. And when this happens GPU load drops and CPU slighlty spikes.

I have no idea why this happens and at first I thought it was game specific so i went to the game forum, they couldn't help me but got me on the right path as i realised while playing rdr2 that the problem was in all games, that load my pc. Then i got a new pc (current one), and thought everything would be solved, but for some reason that one thing, didn't go away, it only got less severe (the lags could last up to 2sec on the old pc).

So at first i thought it would be the power supply that had cuts or something weird, so i plugged into a different outlet, bought new cable extenders, got rid of the extenders so it had direct connection to an outlet, then i moved house, and yet the problem still occured.

Now i have tried disconnecting every bit of hardware one by one to see if my old monitor, or anything else in my setup could for some reason be causing this, as there is nothing showing up on task manager. But once again it didn't work, and the problem persisted.

Afterwards i made a factory reset of my pc to see if it was something i had downloaded, even though no program seemed to show up in task manager, howewer after i did that and ONLY installed Steam, LMU and Logitech G HUB (driver for my wheel), it would still happen.

Finally i have ended up here looking for some hopefully extremely smart people to help me out.

Info on my pc

https://www.userbenchmark.com/UserRun/71634234