I also have had seizures while sleeping. Describing them is a little difficult, but I will try.

I go to bed when I am tired. After about five minutes or so, I fall asleep. Once asleep the action begins, and the scary crap begins. At first it starts out a nice little dream. Then it goes horribly wrong. In an out of body like experience I can see myself having a full grand-mal seizure. I can see and hear everyone around me.

Many of the family and friends around me are crying because of the result of the full grand-mal seizure. At that time I'm back in my body, when I hear my mother crying as she begins holding me. I tell her I'm alright but she continues to cry, and tells me my face isn't. It seems the full grand-mal seizure had cause stroke-like face sagging. But the dream makes it worse. At that time I wake up from my bad dream, so I think.

Soon after I have another seizure. This time it's different. I am conscious, but I can speak or move any of my muscles. I try as hard as possible to yell for help, but I can't get the words out. When I eventually break through, I finally wake up. My whole body is shaking, and I'm covered in sweat.

I just started having these types of seizures this year. So far I've had about five (that I know of). The first (which I described) was the worst, and scariest.