Avoid products with Ivermectin it has been known to cause seizures in some breeds. There are many things that can lower a dog's seizure threshold . Keep a diary of your dog's seizures. Note down anything you have done or that the dog could have come in contact with that day which could have contributed to seizure. It is also a known phenomenon that some dogs may seizure around the full moon.
Vaccinations can lower a dog's seizure threshold and trigger a seizure.
If you feel that this is the case for your dog, ask the vet to split the shots, give them separately at weekly or two weekly intervals and ask for the Rabies shot to be given 2 weeks after that.