Hello,
I have a adult Bullie that has had head shakes for several years. He is almost 5 years old now. This is the simple type of head shake and NOT a seizure or granmal type. This type of head shake/tremor is not VERY common, but common enough in Bullies. Our research found that there are a few common reasons that this can happen.
The main concern is that when this is Happening, is the dog still able to walk, respond and have control.
In our case our dog was able to walk, respond and have control. So we learned what was the cause usually and what helped.
What we found was that THIS big guy didn't like to go outside as much as the other dogs did. And when the OTHER dogs were outside do the biz, they were ALSO drinking water. Well...this guy hardly likes to drink water. So we keep a very close eye on him. What we notice is that when he is having a tremor is when he is NOT drinking enough water. We now keep a close eye on him drinking water and give him his OWN bowl of water in the house so we can WATCH him drink the water.
If he does start to have the tremor, we found a quick cure. Don't laugh. And of course someone will reply and respond that this doesn't work, or that we shouldn't do this. Oh well.
One of the causes that we researched was also due to low blood sugar. So we give him two frozen Otter pops.

I cut the top off, break off a piece and let him chew it. It is cold, its liquid and its sugar. I give him two of them and within SECONDS of giving it to him, he has stopped.
No kidding...I have been doing that for nearly 4 years now. It doesn't happen very often as long as I can monitor when he drinks water. Something about being outside to drink water that he just avoids. Yah, spoiled. I know.
But aren't ALL Bulldogs?
G'Day~