I have the exact same thing. Sometimes I'll go for days with no twitches at all, then it starts up again and I'll have some kind of repeating, fluttering twitch in a small section of muscle. It isn't seemingly related to any kind of muscle use or fatigue or how I feel generally. Usually it is muscles in my back, back of upper arms, calves, etc. It moves around but is usually in only one place at a time. I was diagnosed in summer 04, and have not had a relapse since. It showed up about six months post-diagnosis and has been off and on since - right now I don't have them. Your diagnosis event was a year later than mine so if there is a time course for this symptom, and if you are like me (although not the 42 y/o female part), it will come and go. Hopefully ultimately just go.
I asked the neurologist about it and he said it didn't really mean anything, and it didn't mean that the MS was getting worse. He seemed totally unconcerned about the symptom. Beyond that, he didn't elaborate, and there is surprisingly little information out there that I could find, other than it showing up in early ALS cases, which is an unpleasant thought. However, I've heard of people without MS that complain about the same thing, and there is such a condition called benign fasciculations.
So I can't help much, other than to commiserate and say you are not alone. You could ask your doctor and maybe get some more information than I did. It would be a good thing to bring up. One thing I've started looking into is electrolyte issues (calcium, potassium, magnesium, etc), since there are a lot of associations between electrolyte imbalances and muscle twitching. I'm trying to pay attention to see if what I eat or drink has any relationship to it cropping up. This sounds really strange, but to get a twitch to stop I lightly rub a hand over the twitch, literally tell it to cease and it usually will ease off, at least for a while or it starts up again somewhere else. It is annoying and sort of worrisome at times, especially when trying to go to sleep. Try a light rub and see if that helps it settle down.
Good luck. Do ask your doctor about it when you get the chance. In the meantime, if my case is at all representative of yours, my doctor was right, and there isn't much to worry about with this symptom.