A tremor is an unintentional rhythmic movement of any part of the body. When hands are shaking or trembling, this is typically a tremor of the hands. Tremors are usually caused by problems with areas of the brain that control movements. Neurological problems can cause tremors, but they can also be caused by metabolic problems and toxins (such as alcohol) that affect the brain and nervous system. Shaking hands and tremor can also be a side effect of medications. Shaking hands can occur as a solitary manifestation or can be accompanied by tremor or neurological disturbances in other parts of the body. Depending upon the underlying cause, shaking hands can be mild or severe, temporary or chronic. Shaking hands can occur at rest or during directed movements.