Our 4 year old ds is very happy during the day - outgoing, doing well at nursery etc but every so often (and lots in the last couple of weeks) wakes in the middle of the night and cries uncontrollably - he can't say what's wrong, just "I can't stop crying" it goes on for ages, despite cuddles, reassurance etc. He does it more when we are on holiday - I had to come home a night early from a recent camping trip (not fair on the other campers!) He doesn't show many of the "symptoms" of night terrors, it doesn't seem to be dependent on food, what he has done in the day or anything. Any ideas about what to do??