I have this EXACT same thing. It's kinda just a habit I can't really break.one thing i've been doing for some years now is jerking back my left shoulder, which kinda makes a muffled knacking sound. not sure if that's healthy, though - there's probably something displaced there which just happened at one point.
I have a weird habit of furtively typing the backslash and backspace consecutively, with a few enter + backspaces mixed in.