(SOLVED) Stutters when moving mouse after 20-30 minutes of playing

I have a weird bug in TF2 where the game runs perfectly (144 FPS) for the first 20-30 minutes and then suddenly begins to have stutters(?) whenever I move the mouse or press a key on the keyboard. So far I haven’t been able to isolate what causes the stutters to start, but it’s always the same pattern, with perfect...