I am not sure how it happens, but from one that I've observed with a definite cause,
When I was resupplying my M3 MAAW launcher on the ammo crate on security side in the Map Hide out, game mode skirmish,
I have noticed I became unable to shoot, change weapons, and when I moved, it constantly jittered rather than moving smoothly. It seems like the frame rate is still high so not a performance issue, nor the network, but the movement and screen constantly jumped every 30 cm I moved. This is game breaking level glitch since there seems to be no way of fixing it. It happened to me 3 times over this beta so it is definitely some major bug.
[Not performance related] [Bug] Jitter glitch. (Game breaking)