You can use the Timer behaviour on the star and swap between two timers, on start of layout start timer 1. on timer 1 finished - start timer 2, on timer 2 finished start timer 1.
To actually change the rotation you could use a variable on timer complete setting the variable between 0 and 1. So on timer 1 finished set var to 1, on timer 2 finished set var to 0. Then you can say if var=0 rotate one way and if var=1 rotate the other in a separate event.