Why do they shake?

Dogs do this for a number of reasons. Not only to dry off, but also to remove fleas, dust or other remnants that bother you, to stretch after a long nap or even stressful situations, such as after going to the vet, for example. Another common cause that makes them shake is the discomfort in the ears, either by itching, excess of dirt, inflammation, debris in the ear, among other reasons, especially if the animal has large ears.