Shaking hands and sometimes legs even when not nervous?

i am 15 and i have really shaky hands. they are shaking subtly all te time but sometimes they shake really bad when i'm just doing normal everyday things and even when i'm not doing anything at all. it feels like the shaking is coming from the muscle in my arm. when i get nervous they shake really bad, recently my legs have starting shaking to, i know that many people get this but i am wondering if its normal to have constantly shaking hands.