Essential Tremor (ET), is a nervous system disorder that causes involuntary rhythmic shaking, most commonly in the hands. 
It is especially common when doing simple tasks such as drinking from a glass or tying your shoelaces. It can worsen over time. It is often confused with Parkinson's Disease. It can be severe in some people. It may occur at any age but is most common in those forty and older. 

Simple tasks, such as drinking from a glass or tying your shoelaces may be challenging.  It worsens over time and can be severe in some people. It is often confused with Parkinson's Disease. It may occur at any age, but it is most common in those ages forty or older. Symptoms begin gradually, on one side of the body.
It worsens with movement. It usually occurs in the hands, first affecting one or both hands. 

ET can be aggravated by emotional distress, fatigue, caffeine, or temperature extremes.

Many people associate ET with Parkinson's disease, which includes a stooped posture, and a slow, shuffling gate. ET is not Parkison's disease. 

Those with ET develop other neurological signs and symptoms, such as an unsteady gait (ataxia.).  It mainly involves the hands, legs, chin, and other body parts. Half of ET cases result from genetic mutation. 

Risk factors include genetic mutation. That is, if you have a parent with a genetic mutation for ET, you have a fifty percent chance of developing the disorder yourself. 

ET is more common in those ages forty or older. The condition is not life-threatening, but symptoms can worsen over time. Challenges include holding a glass without spilling, putting on makeup or shaving, difficulty with speech, and writing legibly,

For further information, log on to https://.mayoclinic.org/diseases-conditions/essential-tremor/symptoms-causes/syc-20350534?p=1