Why does my hand shake it has my whole life and iam 25?

Essential tremor. Essential tremor or familial tremor is defined as involuntary rhythmic and oscillatory movements not resulting from other disease or medication. It can start at any age and can be benign or sometimes progress to more serious things. It is typically treated with beta blockers or anti-convulsents. This is definitely worth seeing your doc about so that it can be treated and monitored.