Restless legs syndrome (RLS) is a condition that causes an uncontrollable urge to move your legs, usually because of an uncomfortable sensation. It typically happens in the evening or nighttime hours when you're sitting or lying down. Moving eases the unpleasant feeling temporarily. It might also be tied to: Chronic diseases. Certain long-term medical conditions include RLS symptoms, including iron deficiency, Parkinson's disease, kidney failure or renal disease, diabetes, and peripheral neuropathy. Medications.