I agree that it sounds like a seizure. Sometimes dogs "run" in their sleep, but they would wake when you touch or call them. My saint bernard Zoey (rip) had seizures, but hers were "focal seizures" and showed as teeth chattering. Whenever she would run in her sleep we would call her name and she always woke right up, and that's how we knew she was having a vivid dream instead of a seizure. So the fact that she didn't wake makes it sound like a grand mal seizure to me. Also, the "dazed" feeling you saw is probably post-iptic shock - basically, when you have a seizure, it overloads your brain with more stimulus than it can handle and you experience this thing called post-iptic shock while your brain tries to get itself back to normal. It can last anywhere from minutes to days or even weeks depending on the severity of the seizure.
I would recommend seeing if there is a vet in your area who specializes in neurology.
I have a weird question. What does she walk like? Does she lift her front legs (sort of like a horse's gait) more than your other saints?