I found this interesting article to share: "The points to our dog's wolf ancestors and associated hunting instincts. Although our dogs are domesticated, they still have natural predatory instincts and since they 're apparent in behaviors like pouncing, chasing, and others, including shaking. And with regard to shaking specifically, we can look to wild dogs and wolves that kill small prey by shaking the animal in order to break its spine quickly and end its life. It's been said a dog displays this instinctive behavior in much the same way during play: a dog shakes his or her toy, or "prey" to "kill" it."
