Assuming you do not have the DTs from too much alcohol, or the shakes from too much caffeine or other stimulant it is essential that you see your GP.
This can be a symptom of very minor ailments but can also be an indication of low blood sugar suggesting diabetes, or Parkinsons.
It could also be a sign of stress, tiredness or a reaction to prescribed drugs.
Don't worry about it, but make of note of when it happens, and how long it lasts. The GP will ths information useful.