After rebooting docker node, it will ask to join or init swarm

I have once server with docker as follows.

  • docker-ce-19.03.13-3.el7.x86_64
  • docker-ce-cli-19.03.13-3.el7.x86_64
  • CentOS 7.8 minimal
    I run docker swarm init command initialized docker swarm with one node. Then I deploy a stack of a container using docker stack deploy command. It is working perfectly.
    But the thing is there is a requirement to shutdown server in the midnight and start server early in the morning. The server booting up without any issue. Docker daemon also at the running stage.
    But when I hit docker service ls or any docker swarm related command, it will ask me to join or init to the swarm.
    What was the reason for this issue? I enable the auto-lock feature in the docker swarm, but nothing happens.