My basenji has had two seizures. The first time, I didn’t know if he was choking on something or now, so I tried to sweep his mouth. Luckily, his jaws didn’t clamp down. He had another episode a month later. This time, he was sleeping right next to me on the couch, so I knew what was happening (he hadn’t been chewing on anything or eating).
In the end, take your basenji into a general vet, describe what you witnessed, and go from there. In my case, we were referred to a neurologist, who prescribed medication. We haven’t had any episodes since the prescription was given.
If you witness anything before you can see a vet, the advice given to me was to take video if you can, and cruel as it may sound, stay away from your basenji during the seizure. There is nothing you can do, you just have to wait it out.
By all means, see a vet and get the process going to get a diagnosis and possibly medication.