One of our 3 dogs, Sofia, is an 8 year old mixed breed; probably Pekingese or Tibetian Spaniel mixed with a herding dog. (Yes, she DOES look like an alpaca.) Last night, Sofia all of a sudden, started staggering around. She clearly did not have full control of her rear legs, particularly her rear right leg. At first we thought she’d had a stroke, but that was her only symptom. Very scary stuff! Of course, she did this <Rocket Surgery!> style - following the long-standing tradition in my family that you only develop major medical issues after regular doctor’s hours. So we watched her until she went to sleep, and planned to take her to the vet as soon as they had an opening today.
Naturally, today she is fine. No symptoms at all in over an hour. We’ll still try and get her over to the vet.
So, what the heck happened???
Additional info: She had 10 teeth pulled about 6 weeks ago. Since then, we’ve been supplementing with soft food, since she doesn’t eat as much of the solid food. Could there be a nutritional deficiency due to the change in diet?
My elderly cat had an episode of weakness in her hind legs that cleared up in a couple days. They vet said it was probably a pinched nerve, IIRC, though I did take her for a kitty cardiogram.
Unsolicited advice/ IMNA Vet.
Wait and see. At her age she is a little young for a stroke considering her size. Most small breeds, and mixed breeds in particular live rather long lives as dogs go. My guess is a cramp, or a pinched nerve; like when you turn your neck too fast and get that excruciating pain for minute. If it happens again get thee to a vet. Check her mouth for signs of infection as well, I suppose it’s possible for an infection there to make it’s way to the nerves, but I would imagine that you’d have seen other symptoms before that.
We had a similar experience a little over a year ago. In this thread, the vet had just pronounced a death sentence on my dog. However, a year later, my dog is doing quite well. He still is. Yay! 
Best guess from afar, and from the experience of bundling up a dog and scurrying out to the emergency vet clinic in the middle of the night is that Sofia had a bout of idiopathic vestibular syndrome. (aka idiopathic vestibular disease or disorder)
It’s a malady affecting the vestibular system - the part of the inner ear that controls balance and sense of position (eg: what’s up and what’s down) - and spaniels seem to be particularly prone to it, probably for the same reasons they seem prone to other ear problems. “Idiopathic” is a fancy medical word for “We have no idea why this happens.”
When it’s not caused by an actual disease, tumor or infection, it often goes away just as quickly as it happens. I don’t think the tooth-pulling would cause this, unless she picked up an infection that managed to target the ear.
I’d bet this is it. The vet said bring her back if it recurs. They stopped short of a diagnosis by phone.