i felt like my whole body was vibrating... especially my face and hands???

yesterday i was out at the park having a picnik and all of a sudden it was like that feeling u get when your feet falls asleep... but i got it in both my hands.... the vibrating feeling moved everywhere and even to my face which is what bothered me the most... i even asked my boyfriend if my face was moving and he looked at me like i was crazy... it wasnt... then i noticed tht my hands wouldnt open up... i tried to force them open and it was sooo dificult... this lasted for a good 5 minutes or longer... finally i felt my hands start to relax and my face and everything retur to normal... but it really freaked me out!!! please tell me if i should be worried?