Really fast kick movements! 28 weeks

Vini
Every now and then I feel really strange movements from baby that are super fast. Like 5-6 quick shakes or jabs within a couple seconds is this normal? I don't understand what part of the baby is moving-- is it possible for him to move his hands/legs so rapidly?All other movements and symptoms are normal and good so I don't know if this is something I should call ob about or if the fast movrments are normal?