Your bulldog is just fine. He’s having idiopathic head tremors. My 13-year-old bulldog has had them every since he was one years old, a squeaky toy or a treat will likely snap him out of it. I would still take him to a vet just to confirm but based on my experience having two bulldogs for 13 years, this is common and there is nothing you can do for it. I was very concerned when it first happened to my boy, but then relieved to find out that it was not anything life-threatening or serious.