convulsive,
spasmodic,
spastic affected by involuntary jerky muscular contractions; resembling a spasm; "convulsive motions"; "his body made a spasmodic jerk"; "spastic movements"
fluctuating having unpredictable ups and downs; "fluctuating prices"
palpitant,
palpitating having a slight and rapid trembling motion; "palpitant movements rather than violent eruptions"; "my palpitating heart"
shivering,
trembling,
shaky vibrating slightly and irregularly; as e.g. with fear or cold or like the leaves of an aspen in a breeze; "a quaking bog"; "the quaking child asked for more"; "quivering leaves of a poplar tree"; "with shaking knees"; "seemed shaky on her feet"; "sparkling light from the shivering crystals of the chandelier"; "trembling hands"
quavering,
tremulous (of the voice) quivering as from weakness or fear; "the old lady's quavering voice"; "spoke timidly in a tremulous voice"
