Probably not hypoglycemia, then.
The seizure would occur at the height of the activity.
Did the vet see him after this last seizure? I'm thinking that if he's still walking tentatively and not seeming 'right' after a few days, he should be seen by a vet. Certainly, if he's not had the full thyroid panel done, that's a good suggestion, too--if it
does turn out to be hypothyroidism, it
is something that is likely to get worse as he gets older but it
does have an easy fix (thyroid replacement meds).
Even if he had the thyroid panel done a year ago, he should have another done now. A dog can test normal one year, then show hypothyroidism the next as the condition develops.