It could be bloat - this is a very dangerous problem for dogs, happens more but not exclusively with larger dogs - Apparently it's the second biggest killer of dogs after cancer it's to do with swallowed air (excercising after food or stress can cause it) and the stomach can twist up! Bloat can kill within an hour, please get your dog to the vet right away! I'm not gona blob on any more about the technical stuff, time is of the essence, you can Google it later.
This is not a question
SSS stomach shaking syndrome
It is the dog version of a belly button.
A shaking and retreating dog could be frightened or in pain.
Sniffing.
It is called shaking or drying off!
There are many reasons why your dog could have stomach swelling. Your dog could have a twisted stomach for example.
My dog has been on vitamin K for 3 weeks for ingestion of mice poison. She stopped taking the vitamin K yesterday and has started shaking. She has no signs of bruising (eyes, gums, stomach) but the puppy food that I was giving her the Vitamin K in has made her GI track upset. My vet told me to hold off on food for a day or so to calm her stomach, however, she has started shaking. It is not a hard shake and doesn't do it all the time, but several times through out the day she is trembling. I have an apt to go back to my vet on Monday (2 days away) but I am really concerned. I don't know if she is doing this because her stomach is upset or if it is something to do with the poison.
It likely ate something that upset its stomach, or it could have another painful condition (such as a urinary tract infection) that is causing it to become upset enough to vomit. Take it to the vet to see what is wrong and to get the proper treatment for it.
He is probably just tired just let him rest and give him water. Or it could be the results of your dog having cardiac arrest ( the shaking )
Flogging
He is cold, possibly?!?!?