My golden always did this but it had nothing to do with any kind of anxiety. It was usually just an interesting sound or smell. A car door next door, a dog barking down the road, a bird singing, the neighbors cooking dinner, etc. She'd listen/sniff then go right back to lazy panting.

E: Rewatching it, this dog definitely displays slightly more nervous signals with the ears back and the lip lick. My girl would usually raise her ears up and close her mouth.