This relates to my 4 year old daughter, wakes up every 2 hours and struggles to sleep again.

Some basics: Kids with poor sleep habits, irregular routines or who fight to stay awake are more likely to have sleep issues of various types. Night terrors often occur at 2-3 hrs into the night.They awake fighting & would re-settle into sleep if left alone. If you wake them thinking it is a nightmare they will be confused/difficult. Earlier bedtime & leaving them alone can help this pass. Or see the doc.