Parkinson’s disease is one cause for involuntary movements of the body both localized and generalized. can be due to stress and anxiety, too much consumption of caffeine or alcohol, low blood sugar (hypoglycemia), autoimmune disease like multiple sclerosis, thyroid disorders, nerve compression, and liver disease. Cut down on smoking, alcohol and coffee, if you take them in more quantity. Eat on time. Do deep breathing exercises. Do discuss this with your doctor and get yourself examined. Take care!