Whenever I open my inventory or close it, or open a menu, my cursor does not move for some time (probably less than a second). You can try this yourself by moving your cursor around, pressing E, and observing that the cursor does not move until after a short time has passed.
I've tried seeing if it happens on 1.12.2, but it does not (with the same exact hardware / software setup)
Duplicate of MC-134546.