Not completely sure what causes it (some form of a thread overload when clicking??).
Video: https://youtu.be/zE07I7K_SQk
One way to reproduce: (probably the easiest)
Hold your jump and attack buttons down while against a wall.
Linked issues
Comments 1
UserTeemu
I've also had this jittering when attempting to hit blocks with a sword, while moving, in creative mode.