I had issues with agitation when I went to 100 mg of Zoloft. Not just my legs, but felt like I was crawling out of my skin, like I had to move. It could be something like that. I had issues with myoclonic jerks--where the legs or arms may jerk involuntarily--on Cymbalta (which is an SNRI). I think restless leg syndrome, which sounds like what you have, can be a side effect of SSRIs and SNRIs. So you may need to change medications...