What Causes Frequent Body Spasms?

hi doctor, i am a female,21 years old,167 cm,78 kg,no other illnesses, since 1 year i frequently experience rapid movement (like spasms without pain but very irritating) in 1 different area of my body like my arm or legs ,chest or my abdomen (no specific plase but more in chest and upper left arm) , that is confined to a smal area for about 30 sec. and i can see the movement (like pulse?).

can you please guide me about what it could be? thank you.