I used to go it as a child myself.  I dont know why and I dont remeber walking, I just remeber waking up on my mom's floor next to her side of the bed cold.  I always ended up in her room next to her, and I dont know why.  Now my mom always had are doors opened when we slept.  It was just what made her comfortable so what she bought was and I dont know if you can still get it but you can look into it if you are interested.  If you sleep with your doors opened you can get these little electronic boxes that hang of of the door knob and when you walk past it it would beep.  So my mom could hear it and come and make sure I didn't fall down the stairs.  I dont think it is wise to wake soemone when they are sleep walk just like it is said to be bad to talk to soem one who talks in there sleep.  (which I also do).  I hope this helps if you are interested in the product. 

usually if there is an onset of sleep wlking out of the blue like that it is realted to a problem ,and if you find he has trouble telling you , get him to write his thoughts down at night so that he isnt thinking of them constantly as he dozes.

this will free up his head a bit and hopefully help him.

Try talking to your son to see if there is anything bothering him, or ask him what he's dreaming about - they may be connected.

Hiya guys

My elsdest son sleep walked too and he grew out of it. I took him to the doctor the first time he did it to make sure there was nothing wrong. The doctor said sometimes when kids are having problems at school or anywhere they do this others just dont have a reason so take him to the doctor ask if everything is okay if so just sit back and wait for him to grow out of it sorry I cant be more help have a great weekend

cheers

Angie