My oldest, who is now 4, has suffered from night terrors since around her 1st birthday. The exact symptoms you described, screaming/eyes closed/sweating/scared, are included in the symptoms of night terrors. They are extremly vivid nighmares, in which the child doesn't wake up, though you may think they are awake by their behavior. Anything can bring them on, change in routine, seeing something too vivid or upsetting on TV, etc. Mostly, they come and go in phases. Ours usally last 2 months or so, every 6-8 months. That's the recent schedule, when they first started they were much more frequent. Our peditrician has told us that we just have to wait them out, she will grow out of them. Comfort her, but don't shake her awake or anything- it might scare her more. We also have to watch her "triggers" if something upsets her on TV, it's turned off. Even Disney shows, sometimes the main characters seems in dangerous situations that can upset her- that can trigger the terrors. Check with your doctor to make sure it's not a health issue, but you may just have to wait it out- sorry! I hope this helps!