Restless legs syndrome, or RLS, is a disorder that makes you want to move your legs or other parts of your body when you lie down to sleep. People also describe the feeling as “pins and needles,” prickling, pulling, or crawling. The tingling usually makes you want to move, and that can make it hard to sleep.

Experts don’t know what causes RLS. But it can be triggered by pregnancy, iron deficiency, and certain medicines.