baby isn't sleeping

So my babe is 5 months...EBF and had a routine of going to bed at 8 and waking me up around 1:30, 4:30, 7/8ish to nurse. Starting last week she does her little restless thing in the night so I grab her to nurse before she completely wakes up but when I put her up to me she doesn't want to eat and she is wide awake talking and blowing spit bubbles (yes it's cute)...this has been happening at the 4:30 feeding. She eventually works herself back to sleep but we bedshare so I'm up the whole time with her while she's restless. Any ideas on why she keeps waking up at that time and being chatty Kathy?