My husband and I have two cats.. Dutchess and Yum Yum. We don't let them in our bedroom at night because I don't want them sleeping with us so we close the door. Yum Yum will meow continuously wanting inside cause we are in there and she knows she isn't suppose to be in there.
Dutchess at 4am in the mornings will start meowing still we let her outside so now we have learned to leave her out at night.
YumYum in the morning will meow till she is fed canned food cause it is only a treat for her on fridays.
So maybe your cat wants outside or either in bed with you.