Doing curled up and sleeping is not necessarily because of coldness. It may also be due to habit, self-protection, or physical discomfort. You can observe whether the dog's nose is dry and whether the body is shivering. If so, then it is When it is cold, you can cover your dog with a blanket. If your dog shows symptoms such as low energy and dry nose, it may be sick. You should take your dog to the pet hospital for examination and treatment immediately to avoid worsening of the condition.