My 3 and a half year old wakes up from naps screaming unconsolably

A few times now my 3 and a half year old wakes up from a nap and begins crying for no apparent reason.  Yesterday we thought it was becuase he started coughing and it startled him, but then today he woke up and walked around for a bit then had a meltdown.  The first time this happened was when he was actually sleeping and we had spent the night at my sister's house on Christmas Eve.  We packed him up and were headed to the hospital-he told us half way there that he saw Santa coming down the chimney-so we understood that.  When he screams and does not want to be held-he kicks and screams and I try to offer him things and he just screams longer.  When he was calm we tried asking him questions as to what upset him but got nowhere.  It just breaks my heart to see him this way.  He acts as if though nothing ever happened-almost as if he does not remember that he did that.  

[Natta1980]

My son did the same thing between 3 and 4, now he is better...Chances are that he does not remember that he was doing that...It is sort of a similar to a "night terror"- has to do with moving between stages of sleep-awake....They are very disoriented...My son used to wake up and scream that he wants to go to somewhere.........without specifying where.....The best thing ws to leave his alone (making sure he is safe) - and it would stop in a minute or two. Attempts to talk to him/hold him make it even worse....