What kind of doctor sees somebody for muscle cramps?

Start with internist: An internist is a general practitioner. Problem could be caused by medication causing low potassium, not drinking enough fluids, overusage of muscles, a muscle disease such as pmr etc. If internist can't find cause, consider a physiatrist (specialist in entire musculoskeletal system); or rheumatologist (joint and muscle diseases)., generally, drink more water, eat lots potassium rich foods (fruits).