Thank you for the detailed history. I believe Reggie may be experiencing petitemal seizures. Whereas grandmal seizures commonly present with the hallmark convulsive activity we tend to associate with seizures, petitmal seizures can present in a number of different ways, including: trance-like catatonia, head pressing into walls, and a phenomenon known as hyperesthesia (a syndrome where episodes of phantom pain occur over the rear back, tail, and/or hindquarters).
My initial approach would be to rule out as much metabolic cause for petitemal seizures as possible, namely live, kidney, or endocrine disease, which is easily accomplished by running a general wellness blood screening. If any abnormalities show up that may be associated with seizures, then addressing them may alleviate the episodes you are observing. However, if the bloodwork is unremarkable, then I would treat this case as mild epilepsy, and treat him with an anti-convulsant. Because an assumption of epilepsy based on your history would be a mild form at this time, I would likely choose a well tolerated, mild anticonvulsant such as gabapentin.
Please feel free to discuss my recommendations with your veterinarian.
The symptoms you mention seem like you're there watching him and describing it to someone else. He does have other episodes where he stares in space but does no biting. We'll take your ideas to our local vet. Would this get progressively worse if not treated? We've seen grandmal seizures in another dog we had, even though he was on meds. That was a rough 2 years.
If a mild form of epilepsy, they can progress with time, but not always. If there is a metabolic cause, then dealing with that may be the solution to quelling the issue and halting progression.
Again, best of luck!