Unity Triggering a Method Once Only at the Beginning of the Game - unity3d

Question

I'd like to show dialogue text at the beginning of my unity game as an introduction narration.
I have a method which holds the dialogue text then calls another method which writes the text out to a UI text box. This works fine if I have a button. However, I want it to happen when the scene loads for the first time, but because I'm leaving the scene and coming back within the same game, I don't want to welcome the player back to the scene they just left everytime they reenter.
button => method => another method writes to UI textbox
How could I do this without a button at the beginning?
Code
[System.Serializable]
public class DialogueTrigger : MonoBehaviour
{
public Dialogue dialogue; // array of strings past in
public void Start()
{
FindObjectOfType<DialogueManager>().StartDialogue(dialogue); //find the dialogue manager and plays the startdialogue method I suppose, should do this once the script is loaded because it is the start method
}
using UnityEngine;
using UnityEngine.UI;
public class DialogueManager : MonoBehaviour
{
private Queue<string> sentences;
public Text dialogueText;
void Start() // dialogue manager turns sentences into queue for the sentence input into dialogue manager
{
sentences = new Queue<string>();
}
public void StartDialogue(Dialogue dialogue)
{
//sentences.Clear(); // clears sentences
foreach (string sentence in dialogue.sentences) //each "sentence in the dialogue goes through and enters the queue one by one
{
sentences.Enqueue(sentence);
}
DisplayNextSentence(); //display next sentence method is called once all sentences are in the queue
}
public void DisplayNextSentence()
{
if(sentences.Count == 0) //once there are no sentences left (queue or otherwise?) the end dialogue method is called
{
EndDialogue(); //prints out that the queue has ended... ok
return; // this return is what really ends the dialogue
}
string sentence = sentences.Dequeue(); //new sentence for sentences that are being dequeued...
dialogueText.text = sentence; //dialogue text is supposed to be the same as the sentence that was just dequeued and this should print out to whatever text was assigned to the variable dialogue text
}
Thank you for reading my question.

Answer 1

You should use DontDestroyOnLoad. Create a new script called DialogueTrigger. Then attach it to an empty GameObject in the scene.
using UnityEngine;
using System;
public class DialogueTrigger : MonoBehaviour
{
// Array of strings past in
public Dialogue dialogue;
public void Start()
{
// Keeps the gameobject alive on scene changes
DontDestroyOnLoad(gameObject);
// Find the dialogue manager and plays the start dialogue
FindObjectOfType<DialogueManager>().StartDialogue(dialogue);
}
}