Re: Night terrors or nightmares in 18 month old?
18 months seams a little young for night terrors, but I'm not sure.
My (then) 4 year old had them for a while and they were triggered by changes in routine. She would cry and shake and mumble things, but NEVER would respond to me. I'd cuddle her, rock her, sing to her, say soothing things, and not once did she ever know I was there. She's just continue to shake and cry. Once her schedule was back to normal, everything stopped.
You said your daughter is usually asleep for a few hours before these "episodes" starts. And you said sometimes it's something small like "no no no" and she's back to sleep? If itwere my child, I'd assume she's dreaming about something that happened that day. Maybe she was dreaming about you taking away her favorite toy to put it in the washer, or a spat with another toddler. Maybe she was dreaming about you trying to feed her something she didn't really want, or you ending time at the playgroud too soon.
Again, if it were my children, I wouldn't worry. As long as you're able to soothe her right back to sleep she's prob. not remembering any of it.