Have a sudden movement in my calf muscle at times in the night mostly cause? restless leg syndrome?

Maybe maybe not: Could be restless leg, muscle strain, muscle fatigue, electrolyte imbalance, dehydration, etc.

RLS...maybe: RLS is a common, terribly bothersome, sleep disruption that has unclear causes in most cases. Nocturnal recumbency leg cramps, on the other hand actually hurt("Charlie horse cramp"), whereas RLS gives the sensation one just MUST move the leg/legs. Rarely, electrolyte imbalance can mimic RLS. Interestingly, some anti-Parkinson's disease meds at low doses, are highly effective for RLS.

Muscle: Involuntary movements in muscle can be cramps, fasciculation, fibrillation or myoclonic jerks and may or may not indicate pathologic conditions like calcium or magnesium deficiency or neuromuscular disease. If you have concerns about frequent muscular involuntary movements, consult a neurologist who will order any appropriate tests if needed.