I am experiencing shaking hands or tremor.ive had post concussion syndrome for 3 yrs.not stressed, and don't drink.what could be causing this?thanks!

Various things: A number of conditions can cause tremor in a young person. Some are benign, others are not. Your post is just the beginning of the diagnostic process, not the end. You need to see a live doctor in a brick-and-mortar office so that your doctor can take a comprehensive history and actually look at your tremor. That's ALWAYS the first step.