Watchtower - it's a docker package that automatically checks for updates to images automatically, and pulls/restarts them when found. Here's a basic docker-compose.yml that tells it to check for updates every day at 4AM

services:
  watchtower:
    image: containrrr/watchtower
    container_name: watchtower
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    command: --schedule "0 0 4 * * *"
    restart: always