Needed help identifying the lag

As you may see, from time to time a noticeable lag spike appears (minecraft goes powerpoint presentation mode for around 10 sec, without shaders it drops from 250 fps to 90 fps) and as far as I see it isn't related to any mods except maybe for rendering ones since my fabric 1.21.4 profile has the same problem and there are no mods that add new content. My PC stays below 60 degrees without a problem. Reloading the world almost always removes the lag. I would like to identify the potential reason of this phenomena and the ways to amend it.

(don't mention wonderland.jar, it's profile-specific and unrelated to the problem; it also unknown if it's a game bug or something with my PC so I can't search for specific help, I only need the potential solutions)