involuntarily

To shake slightly because you are cold, frightened, or excited.

To shake suddenly and violently, especially from fear, horror, or disgust.

Refers to a sudden, quick, and uncontrolled movement of a muscle.

Describes muscles becoming tense or rigid automatically, often due to stress or fear.

Used to describe muscles, fists, or teeth tightening without conscious control.

Used for one's eyes or thoughts moving to a different subject or direction without intention.