@LisaMarie Sorry I found this thread so late, but life has been so hectic lately.
Here's a video I took of Maggie having one of hers
YouTube - Maggie
You are going to find a LOT of different answers on here from people whose bullies suffer from these. And none of their reasons are going to be wrong, because I just think that each bulldog starts doing this for different reasons. It's not something that ONLY bulldogs suffer from but they are one of the breeds that are prone to it. So it could be a number of reasons ......
For Maggie it appears to be food, in the video you will see me offering her a treat which in this case is a baby carrot. I can be in the kitchen and cooking with her sat behind me and she is fine. As soon as she believes there is the hint of a possibility of her getting something then the head tremors will start! That's the only time she does it, so there is no treating her with little tit-bits of food when I cook because from then on I'm looking back and seeing what happens in the video!!!
I'll be totally honest with you ... I think they don't really care too much when it happens, and I think the horror of it is only felt by us. I hope this all puts your mind at ease a little.