System (at least GUI) freezes sometimes for 10-20 sec

I did a fresh install a month ago and managed to iron out all minor technical shortcomings myself. All except one: at no particular point (I click a link in the browser or do some GUI stuff in some other app, sometimes I almost do nothing) the whole GUI freezes for 10-20 sec. Sometimes only one window freezes but and I can minimize-maximize other GUI windows. But after ~5sec. all freezes. Strangely it is not 100% frozen (for example some time in the terminal still runs), just the GUI part. Sometimes even the mouse pointer freezes.

Then after ~20sec. it all works again like before. Often carrying out the delayed mouse clicks etc.

What is this? Is this Wayland related? How to I debug such an unspecific problem?

Thanks in advance!
CachyOS is the next level after Linux Mint was king for many years!