Hand tremor is an involuntary muscle movement, trembling, or shaking of the hands. Tremor most accurately refers to a small, rhythmic shaking movement that occurs in a back-and-forth pattern. Everyone has a small, sometimes undetectable, shake when they move their hands. Fatigue, stress, feelings of anger or fear, caffeine, and smoking can make this normal shaking more prominent. Hand tremor can occur at any age but most commonly occurs in middle-aged and older men and women.