for the suspected spinal issue it turned out to be muscular. I was simultaneously getting massage therapy and hydrotherapy that fixed it, whilst the vets were steering towards another 3k of MRI. That was 7 years ago though and he never had any issues on that front since. hope yours is ok
vestibular is a really scary condition initially and can go away after a few days. It just depends what the underlying cause (if any) is. it can be age related or a number of other things.