Offer your group to perform a simple and straightforward body warm up exercises: starting with head and going down through shoulders, arms, back, hamstrings, and calves.
Spread everyone out at the dance floor: explain that there are no right or wrong moves or reactions, and the students should just concentrate on their own performance, trying to avoid focusing on what other people are doing, unless that is the explicit requirement from the facilitator for the particular exercise.
Provide something for your students to think about, triggering the process of their imagination activation, letting them to perform according to the imaginary task, processed in the brain. That may be situation (getting late for the class), sport (playing chess), emotional state (being in love), animal (happy dog), or any descriptive words (raising sun).
If the group is responding well, the leader can give more complicated instructions, offering an additional level or levels of response. For example, chess players might be winning the game, happy dog dropping on the floor to enjoy the paddle, or raising sun is hiding in the clouds.