MonoBehaviour.Invoke

public void Invoke (string methodName, float time);

Description

Вызывает метод methodName по истечении времени time секунд.

using UnityEngine;
using System.Collections.Generic;

public class ExampleScript : MonoBehaviour
{
    // Launches a projectile in 2 seconds

    Rigidbody projectile;

    void Start()
    {
        Invoke("LaunchProjectile", 2);
    }

    void LaunchProjectile()
    {
        Rigidbody instance = Instantiate(projectile);
        instance.velocity = Random.insideUnitSphere * 5;
    }
}