Right? Dogs just don't have it in them to sit still. Everyone knows this, I think. It's one of their most endearing qualities as a species. I love dogs. If you ever need a model for gesture drawings, look no further than a dog. The other day it was really nice outside, so I tied my dog, Mika, to a big tree with her super-long leash and let her enjoy the sunshine and smells and grass while I knocked out some sketches of her antics.
Forget 30 second gesture drawings or even 15 seconds - I don't think she stayed in the same pose for more than 3! It was challenging, but it forced me to grab the most important details quickly; after she moved, I had to flesh it out a little more without the reference. Quick drawings like these are important to practice. It's easy to obsess over getting perfect shapes and outlines, but being all perfectionist like that is a really tough way to work.