I used to get them a lot of the time. It is generally an effect from anxiety, ie. your nervous and anxious about something, so you fiddle, twithch, leg shakes, tap your foot at vigorously, etc etc. You need to treat the anxiety, not the twitch or shakes, as that is the cause. As you said, if you think hard enough, you can stop it. The problem is, as your finding, they will return because your still anxious about something / things in general.

I still do it when I get anxious, though am more cognisant off it today, so I realize when I'm doing it something is making me anxious, and I need to treat the cause of that issue, not bandaid the shakes and tremours.

Why are you anxious? It could be the stuff around your getting with treatment... a most likely cause. This is the stuff that generally precedes being told you haven't got PTSD, or getting stuffed around during the help process... which then brings PTSD out in full flight (as bad as your going to get it), at which point doctors and therapists then go... oh gee, sorry, but I think you do have PTSD after all... my bad! I don't know whether they do this on purpose or what, but it is very very common during the diagnosis / misdiagnosis / getting stuffed around with diagnosis stage.