I think I have head tremors. A movement as simple as raising one's arm requires a communications system more complicated than today's personal computers. Essential tremors are the most prevalent of these movement disorders, but only a small percentage of people with this disorder seek medical attention.
Essential tremors can begin at any age, but usually show up in early adulthood.
They range from almost imperceptible to severe, and can worsen over time. The cause of essential tremors is not known, but the disorder may be inherited. As you suspect, emotional stress, fatigue, anxiety and the use of stimulants such as caffeine can exacerbate the tremors. The tremors usually affect the head and arms and hands, rarely the legs, and can affect only one or both sides of the body. Although essential tremors can cause substantial physical and psychosocial disabilities, many cases of these tremors remain mild and lead to little disability.