Okay. I agree that this does not sound like a typical seizure-like episode, but there are types of seizures that dogs can have, especially upon waking, where they can be looking around and aware of their owner, but stare off into space, or stare into a corner, etc. Your dog is just at the cutoff age where epilepsy can appear for the first time, so that may be a possibility. If it continues to happen I would talk to your vet about possible blood work to rule out a metabolic cause for possible seizures.
Dogs have heightened senses compared to humans, and sometimes they can hear things in the walls/floorboards like mice, bats, etc., so that could be a possibility. They can also hear bugs and such behind walls.
(Now, this is going to sound odd, but as an aside, I do have a friend who had a home where he and his roommate and their friends had all seen at various times a ghost in the house, and the ghost seemed to stay in and around the same room. Sometimes their dog would wake up and do exactly what you are describing, and would always look in the area of that same room, and was very agitated and nervous. I know that might sound odd, but I think that it a possibility.)
I would keep track of these episodes on a calendar so that, in the event that it starts to seem like a seizure-like episode, you can accurately tell your vet how often it is happening. Hope this helps... best of luck!