If you've been known to raid the cookie jar in the middle of the night, down a few cookies, then climb back into bed without remembering a thing, then you somnambulate — you walk in your sleep.
When you somnambulate, your body's on autopilot. Your eyes are open and you look like you're awake, but you’re really sleeping. Somnambulate is a wonderful word, and you may recognize the Latin roots: somnus, "sleep," as in somniferous, “something putting you to sleep,” somnolent, “sleepy, or making you sleepy,” and Sominex, the brand name of a sleeping pill. Ambulare means "to walk," as in amble, “to stroll,” and "ambulance" the vehicle that gets you to the hospital.
