I tend to look for cause/effect relationship. Try altering one variable at a time for a decent period of time to see if there is an effect. Keep a journal of what he ate, activities he did during the day, any stressors (bad day at school, test next day, etc.), when he went to bed, how often he awakes.

I have very vivid and sometimes frightening dreams when I am too hot at night from being overdressed or having too many blankets.

My friend's child had difficulty digesting gluten and woke repeatedly at night.

You may also need to look into a sleep study.

I have a 6yr old boy...he was diagnosed last year with asbergers...he was doing this...night after night....we cut out every tv show or movie that was violent...the dreams slowed way down...apparently they were replaying in his little mind over and over...we also puit him on gluten free diet seemed to help some...unfortunately our new thing is not sleeping at all...ugh!!!!

My little guy use to wake up crying and screaming every night. When he was around 2. Like screaming. Couldn't calm him down or really wake him up. I am certain he was screaming in his sleep and not awake. What REALLY helped him was just stringing Christmas lights around his room. We did it on all four walls by the ceiling. Helped immediately.

My son had one when he was around 3. He woke up screaming and when we went in he said there were bugs all around. We tried "killing" the ones he pointed to but they kept comming so I went and got "bug killer" and sprayed it all around and it killed them all (thank God for Lysol). Luckily he never had another.

Sometimes these can be triggered by something adults would not find worrisome at all. Once my younger son had an attack following a Brady Bunch episode that really bothered him. sometimes they represent really serious daytime problems. My older sone did not tell me that one day care was awful for him. He did not want to bother me. When we figured that one out, of course he went to a different day care.

Sounds like night terrors. I suffered from them when I was young as did my DS when he was little. You are meant to not wake them from sleep if it happens - its hard to watch and sometimes they can go on for like 45 mins. The difference between them and nightmares is that you don't ever remember night terrors.