Highly likely to be an MS thing, I’m afraid, and is called…guess what… “resting tremor”, because it happens when the limb is at rest.
The other kind that sometimes happens is called “intention tremor” - i.e. where you have the intention to do something - e.g. you reach out to touch/grasp something, and instead of the movement being smooth and efficient, your hand (or leg, if you were trying to step onto something) starts to shake.
I think there may be some drugs for tremor, but I don’t have personal experience. It all depends how severe it is, whether you want to bother.
I only have resting tremor in certain very specific situations - the most notable being on the loo, of all places! It seems that something about the exact height of the loo, and where the weight is resting, sets up a tremor in my legs. As I’m not on the loo that much (though it’s getting more), and it can usually be stopped immediately just by shifting my position slightly, I’ve never felt it’s worth reporting, let alone medicating.
It’s been doing it absolutely years - well before diagnosis. I remember one grim night wondering exactly what were the symptoms of Mad Cow Disease, and how many dodgy pies and burgers I might have consumed over the years…before quickly putting it out of my mind.
Little did I know, I did have a central nervous system disorder, so I was closer than I thought. It just wasn’t mad cow/CJD.
The good news is that although it still does it if I don’t sit on the loo exactly the right way, it has never got any worse, and doesn’t seem to have been an omen of anything nastier. It’s just by turns weird, annoying, and occasionally fascinating!