You should see a neurologist. Is sounds like you could have a movement disorder. There is one out there that neurologists always asked me if I had called "Alien Arm". Your arm does things you are not telling it to do. Anyhow, they don't have a clue how to cure any movement disorder, but, it is important to know what it is, if it could progress, and if it is hereditary. Trust me, I know. I have a movement disorder that, came to find out 20 yrs. later, is hereditary. I have children. Scary.
Hi there!
If you are getting extremely bothered by this or this is affecting the way you live, then I suggest you make an appointment with a neurologist. Rare causes of this condition has something to do with a structure in our brain called the "corpus callosum" which connects one half of the brain to the other. If you have a problem with this structure, one side of your body may not know what the other side is doing.
I agree that you may need a specialist. I hope you get to the bottom of this soon.
Regards...