Unless there's a pathological reason behind your shakes, it's probably diet-related. Write down what time of day you are getting these shakes, then write down what you've eaten so far that day. For me, I found that when I didn't eat much for breakfast, then ate lunch with a sugary soda, my hands were almost always shaky. I work in a lab with micro pipetters all day, so shaky hands are really farking annoying.
Anyhow, after you eat lunch, especially if you have a soda or some kind of dessert, your insulin levels are extremely high for a few hours afterwards. This insulin signals your liver to absorb much or nearly all of the sugar that you consumed from your blood, so you end up with low levels of blood sugars, which isn't good for muscle function.
My two cents But write down when you get the shakes and what you've eaten, and see if there isn't a correlation!