The best site I have ever seen on seizures in this one
http://cachins.org/ They do agree that some chinchillas just have untreatable, life long, seizure issues. Although many times it can be a dietary issue. If you haven't read their page you might want to give it a look. They describe what each type looks like to help you know which one yours could be.
You may want to talk with a vet about it. We had a dog that had a problem with seizures. As long as they are short and don't repeat over and over, there isn't really an issue. You just wait it out. However, if the seizure is very long or if they come over and over you need to seek help. Our vet explained to us that extended seizures cause the temperature of the animal to rise. If they have prolonged seizures the brain will eventually fry and the animal will die. Prolonged - like over the course of a few hours.