My son used to have those. He has since almost grown out of them. I think they started when he was around 2 and started getting better around 4. He would be inconsolable, would look through me, didn't want to be touched, etc. It was almost like I would add to his terror when I tried to help and pick him up. While he was going through the terror, he was still asleep (eyes open, walking around, crying) and I became part of the nightmare by trying to get him to interact with me. Sometimes they would last 15 minutes, but sometimes they would be horrible and last for more than 30 minutes. The main thing I was told to do was to make sure that he didn't hurt himself while he was having the terror. (Watch for things he can run into, trip over, etc) Just watch over him to protect him and don't try to force him to wake up. As painful as they are/were to watch, once they were over, my son would sleep soundly and not remember them in the morning.