I've done some sleep walking as an adult (though my sister was the one who had it *bad* as a child.) It's a bit dangerous with a toddler, so I would be a bit concerned, though there is nothing you can really do to stop it. When I, personally, have gone through periods of sleep walking and had incidents of sleep paralysis and night terrors, it was because I was over-tired and stressed. I doubt a toddler is experiencing as much stress as I was during those periods, but it wouldn't hurt to make sure he's getting enough sleep and is not over stimulated before bed time. Just make sure the room is very, very safe and he can't get out of it. Many children grow out of these things, though in my family, we all did them long past childhood. I seem to recall my parents attaching something like a bell to our bedroom door as children? This was after my sister was found standing in the shower, soaking wet. There must be something better available now - and if he's in your room, you could just lock the door.