Playerreadyscene.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class Playerreadyscene : MonoBehaviour
{

    public string mainMenuName = "SampleScene";
    // Start is called before the first frame update
    void Start()
    {
        StartCoroutine(Go());
    }

    // Update is called once per frame
    IEnumerator Go()
    {
        yield return new WaitForSeconds(3f);
        SceneManager.LoadScene(mainMenuName);
    }
    //when the player ready scene appears, then it will start the coroutine that brings it to the main scene
}