goldiesplash, do an internet search for Vestibular Disease, or as it is sometimes erroneously called, Geriatric Vestibular Disease. It is not confined to old dogs. The symptoms are similar, see if any match what your dog is showing. My sister's dog had it when he was 12. Apparently onset is typically very sudden and so is recovery. TRue to what Sis's Vet said, it might last a month to 6 or so weeks, bang on a month Laddie just stood up and walked again. Laddie recovered fully except for a bit of heat tilt which diminished in his remaining four years of life, yes, he lived well past 16.
This is often confused with ear infections and epilepsy so you might want to search up information on them too.