Possible Clues:

• Shake involuntarily
• Show fear, maybe
• Quiver or quake
• R.E.M. belt out rock
• Shiver slightly as with cold
• Be agitated when it's three times the figure entered
• Robin's quiver might cause his enemies to do this
• Shake (with fear)
• Shake medicine initially - pour it into very large whisky!
• Quaver, a bit of music included by singer