try looking up Essential Tremors on the internet. My son was first diagnosed at 16. Its not very common but reasonably harmless. Sometimes he doesn't shake for days then others he can't hold a glass of water hardly. Its only really noticeable in my son's hands, he doesn't shake elsewhere. He has seen several docs and a neurologist and had tests. They all confirm Essential Tremors, which as I say can be somewhat annoying, but my son has been told it may never get any worse and its harmless i.e. you don't die from it and its not as debilitating as PD. Hope that helps.