Embodied forms of representation like gesture have been shown to play an important role in how learners conceptualize phenomena in physics; however, we know little about how students use gesture to capture the idea of "instantaneity." Drawing on multimodal microanalysis of interaction, we examine how undergraduate physics students use representational gesture to make sense of instants or single moments in time while modeling energy dynamics. Our analysis demonstrates how students use four different forms of representational gesture to capture instantaneity: These include (i) looping and replaying a physical action, (ii) showing a tiny subinterval of time, (iii) freezing a frame of an action, and (iv) marking a boundary location on an imaginary timeline. Implications for physics learning are discussed.