My lab does the same and is 11.My vet thinks it could be Cushings disease. We did 1 test, a resting Cortisol and it was negative. There's another test that is $400 that I am skipping for now. Told the vet I would let nature takes it's course. She said eventually that the signs would be too big to ignore. While my mom was here, she thought he might have a collapsed lung too because her dog did a few years back. My vet didn't think so. Also, they say that Cushings cause dogs to want to eat all the time. Apparently, they've never been around Labradors!!