When our boy, Lujan, was having siezures, our vet told us they are more susceptible to them when they are excited ie: when they're having dinner - and that fitted perfectly with ours. We spent may occaisions fishing mouthfuls of food out of his mouth and throat while he was siezing.
Good luck with your doggy. I hope any meds he gets put on help him. Just make sure if he has one when you're around that there's nothing he can hurt himself on - that's if he starts to thrash, and give him lots of cuddles and reassurance when he comes around. It can be a bit scary for them too.
Julie.