Chloe ( who is 10 months) has started doing this also !
Both my dogs are crated at night ( well Chloe is in her playpen ) and they usually go to sleep just fine , but at around 5a.m Chloe starts barking like a little nut
( luckily their room is on the other side of the house so it's very faint )
I know she doesn't have to potty because she uses potty pads which she has in her pen with her , their room is warm so I know she isn't cold , and she can see Sydney so I know she isn't lonely...so I have no idea why she barks except she is done sleeping and just wants to get up and play.
I don't want her sleeping with us ( our bed is very high and I'm afraid she will fall out and get hurt) so dh is going to sound proof their room
then they can just annoy each other and not us
Maybe you could get a bigger pen and use puppy pads and see if that stops her , she may just have to potty and with the pads she wouldn't have to wake you.