B.K.
He's getting older and he's not getting enough exercise probably. Labs need to go for several walks a day and they need to PLAY. Just like toddlers. When he was younger he slept a lot and was probably content. Now he needs exercise. (He also doesn't need a bark collar. They're inhumane.)
Just like a baby, he is trying to tell you something and all he can do is bark. Take him to training classes somewhere, like Petsmart, and learn how to be a good dog owner. And also, find a place to let him run at night before you go to bed. Sounds like he's lonely, and bored. Maybe he could sleep with you, instead of in the kennel.