tremble B1

/ˈtɹɛmbl̩/ To shake slightly, especially from fear, cold, or strong emotion.

tremor B2

/ˈtɹɛmɚ/ A slight shaking or quivering movement, often from fear, illness, or weakness.

trembling C2+

/ˈtrɛmblɪŋ/ shaking involuntarily, as from cold, fear, or weakness