maybe its kinda wrist equivalent of shin splints...I dont know if thats a medically sound explanation. But I have had pains in my shins when walk at times and this sounds similar kinda pain you speak of.
My right hand tends to shake uncontrollably if, say, I have been polishing the car, and then try to hold a glass of water. I do a lot of typing for my job, so I guess it could be RSI.