i know how annoying and frustrating that can be
Are you on any stimulants, or any kind of natural stimulants (coffee, caffiene, chocolate, etc.) ?
Have you been seen and checked out by a neurologist? (if not, that could help a lot in finding out the true cause, and the treatment. and if yes, then i would suggest getting a second opinion from another neurologist )
It could be something related to the meds, or something that was caused by the meds that remain even if you currently aren't taking the med that would/could be causing this. but even in that, it would still be best taken care of through a neurologist.
a pdoc and a neurologist are closely related in what they do, but they do separate things. such as a pdoc would likely see this as anxiety and try to fix it with meds. but if it's not anxiety, then he or she would only be treating it as what it appears to be. (in simliar example, what people often think when they see a child acting out, is that it's a temper tantrum. but the kid knows that its a meltdown (maybe not in labels, but knowing how one feels compared to the other), and others may try to treat it as what it appears to be (a tantrum), when it's actually a meltdown).

another example would be me being a kid, and having stomach pains. the doctors did xrays, and CBC tests, and since both came back fine on every many one of them, they wrote it off as a 7 year old who was having anxiety.. and it kept being that.. although i knew when i felt anxious later on, but wasn't anxious during tummy pains.. it appeared to be anxiety to them.. but it wasn't until i was hospitalized in the ICU at age 23 that when a GI doc came and did more than just those simple tests, that i had crohns, and ulcer colitis. and not only was it incurable, but also the damage what had already been done, couldn't have been undone. (what the gi doc told me). so if they not accepted the reason to be anxiety, they would of found the reason to be something that could had been kept from getting any worse. something the gi doctor also told me was that "from now on, if you know that something is wrong, and the doctor can figure it out, and thinks that it's nothing, or something that it isn't-and you know if it isn't. then he hasn't done the right test to find the answer." (i know that is a bit of an extreme, but i think it still can relate to whats going on in your situation).

The first two things that pop into my mind when i think of being shakey and trembling (and knowing it doesn't feel like anxiety), is stimulants, and neurologist.

(altho i'm not a doctor of any kind, so... what i say shouldn't be taken as a diagnosis, or accuracy. but just as a suggestion).