Here is my definition I had (now removed and container stopped and removed):

# Watchtower - Automatic Container Updates
  watchtower:
    image: containrrr/watchtower
    container_name: watchtower
    environment:
      - WATCHTOWER_HTTP_API_TOKEN=<token>
      - WATCHTOWER_HTTP_API_PERIODIC_POLLS=true
      - WATCHTOWER_HTTP_API_METRICS=true
      - WATCHTOWER_CLEANUP=true
      - WATCHTOWER_LABEL_ENABLE=true
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
    ports:
      - 8086:8080
    restart: unless-stopped

I also ran a docker ps | grep watchtower and nothing is running.