I had trembling come out of nowhere and it lasted for a couple of months! I had nerve conduction studies done and bloodwork and everything and I was put on a tranquilizer and Zoloft. Eventually it went away, and only comes back for very short periods of time (a few minutes sometimes). I have had generalized anxiety disorder and panic attacks for about 18 years.
You should ask your doctor for some quick acting anti-anxiety medication like xanax, and use for a short time, then switch to klonopin for another short time, a week or two,consider seeing a therapist to understand the origin of this symptom...
Unfortunately that is how it happens. No triggers , no warning, it just hits. I have had panic attacks for the last 2 years and it can consume your life. You can either self medicate which just covers the problem, and actually makes the attacks worse once you become tolerent of the drugs, or you can seek mental health help. I am seeing a therapist and my attacks are down like 80%. I would not wish these attacks on anyone. They can become debilitaing. Acknowledge them now and seek help!! There are so many of us out here and this is a club where we need no new members!! :)
Take care and good luck!!