With command blocks join title?

I have a Minecraft server in 1.16.4 and want to make a join message when you come to the server. I already have an animation. The animation should appear when I join but not when standing on a pressure plate or a certain block.

If it should be a plugin then the following code:

import org.bukkit.event.EventHandler;

import org.bukkit.event.player.PlayerJoinEvent;

public class JoinListener extends MasterListener {

@EventHandler

public void onEvent (PlayerJoinEvent event) {

// Orders when a player joins

Unfortunately it shouldn't be a plugin, I mentioned that too

Then unfortunately I don't know how to do it.

OK