Hi and thanks for the query, It is useful to know if this is pain, the duration, any identified triggers and the usual symptoms that accompany this muscle pull. In some cases, especially when of short duration and painless, its due to abnormal excessive electrical isolated muscle excitations. The cause not generally known, but the outcome is favorable and actually has associated complications. Ion or electrolyte abnormalities could be a source in other instances. Low blood Calcium, Vitamin D and Magnesium are commonly incriminated causes. I suggest you consult an internist or neurologist for a critical assessment. Thanks and kind regards. Bain LE, MD.