Gibbs did this to us a bit ago (I guess it was during my Christmas break). We took him to the vet and they ran all kinds of tests and found NOTHING! The vet said that she too had a dog that used to do it without any tests showing the cause. Hopefully this will be a one time thing for yours too. I have to mirror Mikey T when I say that you should not put your hands in the mouth (unless you're willing to loose a few fingers). Just like when humans seizure the best thing you can do is move things away from them so as they will not hurt themselves during the seizure. They will work themselves out of it, though I know it is very scary to watch. I grew up with a kid that had seizures daily so I know how hard it is to watch and do nothing. I totally brokedown and freaked out when Gibbs did it. Good luck in finding out whats going on, and keep us posted.
~Heather
~Heather