This is a common occurrence among infants because their central nervous systems are in such an early phase of development. It does not invite alarm. Of course, you should confer with his pediatrician. We always suggest people do this and not rest with posting a queastion on this Forum or on any other interne site.
RLS is not a condition that affects infants.
I am an adult and I get these involuntary leg jerks too because I have RLS or "Restless Leg Syndrome". Not sure if this is common among infants as well, but RLS affects billions of people from what I hear. Go see your pediatrician about this just to be sure it's not RLS.
Thanks a lot for the advice