I took 200mg of Zoloft daily around the age of 14-15, and developed shaking in my legs (like I'm bouncing my legs up and down impatiently, but not consciously). I am now 24, no longer on Zoloft for many years, and my legs were shaking as I wrote that last sentence. It doesn't hurt, I don't feel like I'm expending energy, most times it happens (I have maybe 2-5 episodes a day, unless I'm very anxious about something) I don't notice it, and it stops after a few minutes. They're stationary now. Most last a few seconds, some last a few minutes, but not often. I'm really not bothered by them at this point any more.
If I'm sitting in a chair where my feet don't fully touch the floor (I'm 5'2, it happens), an episode can be set off by that. If I sit forward and press my feet firmly and flatly onto the floor, I can stop it.
It does not happen while driving. Not even in my left leg.
So, I don't know how much help that was
but there you have it.