Algos work in a linear fashion, so it is not possible to set a direct "loop."
However, you can link to another Algo, or even to the top of the same Algo. For more, see here. For example, if you're building an asthma pathway and are asking the clinician to "step up therapy," you can have the user re-start the algo, with a "default selected" therapy choice, bringing the user directly into that part of the pathway.