Night waking

A few years ago, my middle daughter suffered from night terrors. Which, if you don't know, are not the same as nightmares. Nightmares are bad dreams that, sometimes, wake you up. Night terrors, on the other hand, are when a person screams, cries, walks, runs, and so forth while not fully awake, generally feeling scared or even terrified. My daughter used to wake up screaming, talking but making no sense, yelling for me even when I was holding her, and, sometimes, trying to run out of the house. It was frightening. At the time, the doctor told us that he believed she was having night terrors as a result of turmoil in her life. It made sense--her father and I had just divorced, we moved to a new town, she was attending a new school--yes, this was turmoil. The doctor explained that my young daughter was stressed and couldn't deal with all the feelings she was experiencing while awake, so these feelings and stress manifested themselves in the form of night terrors. The doctor indicated that she would probably just grow out of it. She did. After a few months, they simply went away, and she slept fine every night. Now, my same daughter is waking up often at night. She is not having night terrors, thank the Lord. This time, she is getting up, sometimes crying a little bit, sometimes saying she is scared, but mostly just walking around and talking but not making any sense. I cannot think of anything stressful that is occurring in her life or in our family right now. So, I am puzzled. Do some kids just experience sleep-walking and night waking for no real reason?