In general, dogs sleep 15 hours every day when they grow up, so you will find that as long as dogs are bored, they may be sleeping. Even if he gets enough sleep at night, he will take a nap during the day.
It is found that dogs are mainly divided into shallow sleep and deep sleep on the water. It is easy for them to wake up at any time when they have a light sleep, which is also a primitive instinct to stay alert. When a dog sleeps, his body will relax, his hands and feet will twitch slightly, and sometimes he will sleep on his stomach and moan slightly, which looks a bit like a person dreaming.
Dogs will find a quiet and comfortable corner when they sleep, and then have a good sleep. However, dogs can only really rest when they are asleep, and most of their sleep is shallow sleep. So dogs don't really have much time to rest.
Extended data:
The explanation of sleep:
Puppies and old dogs sleep longer, while puppies and strong dogs sleep shorter. Dogs are generally in a shallow sleep state, and they can wake up with a little movement, but there are also deep sleeps. When sleeping lightly, the dog is prone, with his head bent between his two front paws, often with one ear close to the ground.
Dogs are not easy to wake up after a deep sleep, and sometimes they talk in their dreams, such as barking and moaning, accompanied by convulsions of limbs and shaking of their heads and ears. When you sleep, you often lie on your side and spread out all over. It looks cheerful.
Dogs are not easily awakened by acquaintances and owners when they sleep, but they are still sensitive to strange sounds. Dogs are often in a bad mood after being awakened from sleep, and they are very dissatisfied with the people who wake them up. Dogs that just wake up are blindfolded, and sometimes even their owners can't recognize them. So its dissatisfaction will sometimes be vented to its owner, such as barking at you. Don't wake it up because of boredom or mischief.
References:
Baidu Encyclopedia-Dogs (Canine Mammals)