There are a couple of things to ask yourself here if your dog is shaking and struggling to walk:
- Is it possible he ate something like a poison or toxin?
- How long have the symptoms been going on for?
- When did he last eat?
- Are his gums pale or pink?
My advice would be to get this information together and get on the phone to your vet. They will most likely ask you to come in, as this sounds pretty serious.
We could be talking about any of the following conditions:
- toxicity/poison ingestion
- cardiovascular disease
(low blood sugar)
- organ system disease
The only action you can really take for certain at this point is to book a vet appointment ASAP.
Also as a precaution rub some pancake syrup or sweet syrup into his gums in case of low blood sugar.
Good luck and let me know how this turns out