I have a Peantus cartoon strip clipped out of the paper from many, many years ago. Each panel shows Snoopy sleeping, in a different position, curled up, stretched out on his front, on his back with his paws in the air. In the last panel, Charlie Brown is explaining to his teacher that he didn't do his homework because he was too busy watching his dog sleep.
I could say the same, just watching mine. Rupert had his chin draped over the edge of the bed, so as he fell deeper into sleep, his head lolled forwards, and the motion awoken him a little. When that happened, he wagged to himself and then fell asleep again. And then his head dropped again and he was awoken again and he wagged to himself again and the whole cycle continued. I never saw a dog who enjoyed napping so much that he'd wag in his sleep.
The cats must have been on to something a long time ago. Catnap is a legit word, but not dognap. And kidnap is a bad thing for kids.