Sleepwalking is common in children and subsides as they grow. Some causes for increased frequency could be not sleeping enough (sleep deprivation), certain stimulants like coffee/coke etc. There are usually no underlying psychological issues.Make sure that your son is getting enough time in bed. Avoid any activity prior to bedtime and completely eliminate any kind of stimulants. Also, make sure that there are no obstacles in the path that he sleepwalks; especially sharp things that may hurt him. If he continues to have frequent sleepwalking despite simple measures there are medications that may help. In such case you can take him to a paediatrician who can start him on meds. However, I strongly suggest that you take the simple measures prior to considering medications.