My doctor told me that an occasional twitch is normal and part of "falling asleep." If you're referral to occasional twitches, like one or two per night, I wouldn't worry. Check out "hypnic jerk." The cramps sound like Charley Horse's. You may want to read up on them. They are excruciating.

RLS is more of a compulsion to move your legs to relieve discomfort of tingling or other sensations. But it goes on for a long time (vs. one or two twitches) and is very disruptive to sleep (at least in my case). But with RLS, you move your legs because you have to in order to relieve the discomfort. The hypnic jerks are involuntary.