Create a single instance of your motion using keyframes. Open up the Advanced Motion Lab, and shift-click on name the object in question. A pop-up will appear, with one of the choices being "make repeat". I believe that if your movement sequence is shorter than the entire animation duration, it will just repeat the sequence for the rest of the duration. It uses all keyframes from the beginning of the animation to define the "repeating sequence". Or, you can make a sawtooth wave in the Advance Motion Lab, and stretch your keyframes out over the entire animation. The other way is easier.