Mouse jitter

I've been having a weird issue recently, here's all data I could gather. The point of the issue is, sometimes in game my mouse starts jittering, freezing, responding very slowly sometimes with up to 3seconds delay. It's not by the mouse, I've tried several and also mousepad on laptop with no variation in the issue, when the mouse is stuck the delayed response applies to keyboard too, so I might tap tab and the score table is shown for few seconds nonstop, so it's moreover regarding all sorts of input on the pc, FPS and ping stay normal during this, doesn't seem to be bound with this issue It happens only in LOL in-game in all game modes, rift, Aram, TFT, doesn't happen out of game, doesn't happen in other game or in any other software at all. only happens in certain period, it's about 10minutes into the game or around first carrousel round when it starts, duration carries greatly but seems to be affected by PC's performance (someday it's just a few moments, other days whole minutes, one way or the other in back-to-back games the severity and duration of this period is very alike) so it's all delayed and jittery like this for the given duration,then it sometimes just end, other times it's literally beeps out, (kind of beep like when you press too many buttons at once on an old pc and it can't handle so many proccesses), and then everything works normally for the rest of the game, seemingly regardless of the games duration.

Now it appears to me, strongly suggested by the beeping part, that it might be issue in the PC, weak process (I have weak PC, but low spec mode and most of needless features like hud animations turned of), but then it only happens ONCE per game, and only in league, I ran more demanding software with no issues of this sort at all. I read somewhere it might be a difference in mouse sensitivity in game and windows in old thread, there was a guide to reset input setting by deleting section of input.iny file, did that to no success. most of my mice have adjustable DPI, but I tried it with cheap unprogrammable mouse too with same results, plus the lags affect not only mouse cursor, so I guess there's no single external device to be blamed. Reinstalling client doesn't seem to do a thing either, though I might try that again. This should be all I know about this, I hear there are a lot of people with similar issues, so let's fix this