Dogs will fall into a deep sleep after falling asleep for a period of time. This phenomenon is actually the same as when humans sometimes shake and shiver while sleeping. It may be due to dreaming and trembling legs. Parents do not need to worry too much about what is wrong with the dog's body. ,it `s just normal. But there is another possibility that the dog is shivering due to cold. At this time, measures need to be taken to keep the dog warm to prevent the dog from catching a cold.