I have a 9 year-old husky-lab mix who has always been pretty healthy and we had a sort of similar experience with him. He has had 2 or 3 incidents over the last year where he is laying on the ground and his legs start spasming. He never loses consciousness or control of his bowels/bladder, just has a scared and confused look in his eyes. This lasts for about 20-30 seconds maybe. He's then unable to walk for a 5-10 minutes afterwards, and then when he is able to get up, he's somewhat unsteady or weak for another 30 minutes or so. After that, he seems perfectly fine. Twice we had him in the car to take him to the vet, when he suddenly seemed perfectly normal so we didn't end up taking him. During his routine vet visit we mentioned it. The vet didn't think it was seizures. She recommended possible imaging, but we didn't want to be too aggressive with any treatment, so we just got him some pain pills in case he had another episode. I don't think he's had any issues in 4-6 months or so, so I'm hopeful it's not some intracranial mass or something. Scary as hell though