Did you ever find a reason for your dog to be dizzy? My dog has the exact same symptoms. Once or twice daily he gets dizzy and paces. The dizzy spells only last a few seconds, but during that time he jerks and loses control of his hind legs. Then he's fine for a few seconds and then he's dizzy again. The entire episode usually lasts 5 to 10 minutes and then he is completely fine (he is 14 by the way). If I can get him to lie down, the episode is usually shortened. He has a heart murmur, but the vet said that his heart problem should not cause the symptoms that he is having. I've taken him to the vet 3 times and they run blood work every time which always comes back normal.
Last month my dog woke up, jumped off the bed, twirled in circles and then he was having trouble with his rear legs. Then he sat and shivered and then he was fine. Day before yesterday my dog looked a little wobbly and he came up to me for comfort and then lost control of his bowels while he was quietly standing there. He wasn't even aware of it. I took him to the vet yesterday and they tentatively diagnosed epilepsy but they are pretty sure that is what is wrong. I am so sad, I was searching online before I took him to the vet and I thought your dog's problem sounded a lot like mine. Today I went looking for your question again to tell you what happened to my dog and suggest you take yours to the Vet just to see.