My 4month old wakes up 90 minutes after bedtime

LOLIA

My LO is 4 months old and takes 3-4 naps a totalling 3.5-4.5hour. She wakes up at 9am every morning and sleeps at 9pm. However, lately she wakes up crying 80-100 minutes after bedtime. I usually have to feed her and then she goes back to sleep and wakes up after 4 -5 hours for a feed. Does anyone have this experience. Any ideas how to prevent this?