One of the most common cause is hypoglucemia. Does the dog have these while at excercise? or at rest? If hypoglucemic blood tests when normal would not necessarily reveal the problem, when blood sugar returns to normal, tests will be normal as well. Diet may be a factor, but more likely it is frequency of feeding, usually the hypo dog needs feed more often in smaller quantities spread throughout the day. Did you check on EIC? Irregular heart beat can produce seizure like results, as well. As suggested the inner ear can do this. Ingestion of crayons, which the dog cannot digestively process, can do this. Any youngsters in the family where the dog could eat crayons or play dough? These are all issues which can produce these symptoms. I have seen all these cause the symptoms you describe. I've seen it so bad a guy had to carry his dog out to the car, approximately two miles. As suggested, if it's genetic, which would be my last guess, despite the admirable qualities of the dog, you don't want to breed this into continuing generations. Good Luck and keep us posted.