rattle (one's) cage
To purposefully anger, upset, or unnerve one, especially to affect their performance or undermine their credibility. He makes a point of taunting his opponents before each match in order to rattle their cage. The audience member asked a number of embarrassing questions about her past in an obvious attempt to rattle her cage.
ˌrattle somebody’s ˈcage
(informal) annoy somebody: Who’s rattled his cage? OPPOSITE: smooth (somebody’s) ruffled feathers