earthair
First things first - look for the obvious which could cause sleep disturbance or nightmares. Assuming he agrees to your help, go into the room at night (before he goes to bed so he's not there) and observe and listen. Does the traffic going by outside cause lights to flash across his face or at a mirror? Are there mirrors facing the bed? Odd plumbing noises? Wifi or electrical devices left on? Standby lights flashing? Terrible feng shui? If he'll let you, lie on his bed. What do you feel? Do you feel safe and relaxed?