If someone is fidgety, their body will not stay quiet. They tap a pen, swing a foot, shift in the chair, pick at a sleeve. The usual reason is boredom or nerves — a long class, a wait outside the dentist, a talk they do not want to give. It is a slightly critical word, but a soft one: teachers and parents use it about children, and people use it about themselves with a small apology. It names the restless movement, not an illness. Though actually, a fidgety person is not always being naughty; sometimes they are trying to think, or trying not to show they are worried.

坐不住、靜不下來（因為無聊或緊張）