Its very hard when they're so young going through something you can't do anything about.
Our son has been normal every day after a NT. I did notice that in addition to being overtired, if he is over stimulated he will have one. We're on vacation now visiting both sets of grandparents so his schedule is off, he is being held more often and its hard to keep it quiet in the evening. I'm guess this is why he has had more in recent weeks.
I don't know if this has anything to do with NT but our son is also easily frightened. He also had one during his day time nap. If I hear him wimpering (a sign he is going to have one) I will try to wake him up and have been sucessfull with this. Also on my husband's side of the family there's sleep walking and sleep paralysis - if you do a google on it you will find them closely related.
His pediatrician said it was nothing to worry about and that it was something that frightened him (dream) before he went into deep sleep. I've done more research since then and found that when you're over tired you will go right into deep sleep and your body doesn't have a chance to shut down properly which can cause a NT.
either way its scary not knowing but I'm beginning to handle them a little better although I think I've aged 10 years in one month
hope this helps