Is your dogs making paddling movements with it's legs like it swimming but not in water? Could be a seizure.
This could be a very serious reaction to something. Did you recently give your dog an over the counter wormer or a flea and tick product or anything else? Could your dog have gotten into anything it shouldn't have? Is it a young dog and/or lacking in the vaccine area (and not even that's a guarantee) since parvo or carona could be a concern. Have you found any ticks on your dog recently? It could be any number of things. Since many of those can kill your dog you probably want to at least call your veterinarian and see if they think you should go in(which is likely).
Your dog may have parvo
Does it have a disease like rabies? Maybe its sick take it to the vet asap!
Has she gotten into a fight with any squirells or racoons lately because that sounds like rabies