This might have been resolved through this already:
I originally thought I was having a bug in my game, but many other devs have confirmed they are reporting the exact same issue.
This issue appears to happen seemingly at random when fairly vanilla character models are just standing still.
Characters are shaking as if their orientation is struggling to act correctly. This is causes some strange flickering that also shakes the camera as a consequence.
The physics also appears to act a bit unusual as a result.
Additional, characters jump much higher than intended.
Notes:
Modifying their humanoid state will fix it temporarily.