Both of my children had night terrors beginning around 14-18 months old. There can be environmental triggers to them and they are also tied to the sleep cycle. So if your daughter is having them every hour for a few hours, that sounds consistent with a trigger.
Check the temperature of her room, if it's warm, try cooling it down. If it's cold, try warming it up.
Are there any ambient sounds outside or within her room such as a fan blowing, a white noise machine, crickets outside? Even if she is falling asleep and staying asleep with or without certain noises, having them (or not) during the second half of her night's sleep could be triggering a night terror.
Her sleep position can trigger a night terror. Sleeping on her hands or her hand falling asleep under her head, a pain or pinch in her neck or hip, a pajama leg cuff that's slightly too tight. This one is more difficult to control and because your daughter's are much more consistent, this doesn't sound like the trigger. But it absolutely can be part of the problem.
As you're experiencing this regularly, you've probably already learned some tips to help reduce the length of time that a night terror lasts. But just in case, here are some things I've learned to help reduce the length of a terror.
- Don't try to wake your child up.
- Offer a consoling hug or hand hold as long as it doesn't escalate the terror. Sometimes the best thing to do is to be close but not touch your child at all.
- Remove blankets or other objects from the immediate area.
- Utilize soft voices or sing quietly so your child's subconscious recognizes your presence. The point is to be reassuring without trying to wake your child.
Best of luck! Night terrors are hardest on the parents and can be quite scary and exhausting to deal with. Thankfully our little ones don't remember them and it doesn't have a negative impact on growth or development.