It happens to me every time I become very anxious, and is usually a precursor to a panic attack. Typically, for me, it starts as internal shaking, and then progresses to visibile shaking in my hands.

The shaking is most definitely a symptom of anxiety. I've found, for me, that if I can stop, and focus on taking deep breaths for a few minutes, the shaking will subside. It's basically a reaction to an excess of adrenaline as your body prepares for flight or fight.