Trigger the dialogue system

Hi there. I wrote the code which should be triggered by trigger but it works before I trigger the trigger.
It’s just that I think I wrote everything by logic, but apparently, I did not. Thanks in advance if you help me.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using TMPro;

/// <summary>
/// Simple dialogue system. No choices. 
/// </summary>
public class Dialogue : MonoBehaviour
{
    [SerializeField] TextMeshProUGUI theText;
    [SerializeField] string[] sentences;
    [SerializeField] float typeSpeed = 0.02f;
    [SerializeField] GameObject continueButton;
    int index;

   
    private void OnTriggerEnter(Collider other)
    {
        if (other.tag == "Player" && Input.GetKeyDown(KeyCode.E))
        {
            StartCoroutine(StartDialogue());
            
        }
        
    }
    private void OnTriggerExit(Collider other)
    {
        if(other.tag == "Player")
        {
            continueButton.SetActive(false);
        }
    }
    public void NextSentence()//button func 
    {
        continueButton.SetActive(false);
        if (index < sentences.Length - 1)
        {
            index++;
            theText.text = "";
            StartCoroutine(StartDialogue());
        }
        else
        {
            theText.text = "";
            continueButton.SetActive(false);
        }
    }
    IEnumerator StartDialogue()
    {
        foreach (char letter in sentences[index].ToCharArray())
        {
            theText.text += letter;
            if (theText.text == sentences[index])
            {
                continueButton.SetActive(true);
            }
            yield return new WaitForSeconds(typeSpeed);
        }
    }
}

Looking at your code, it looks like it would only start the coroutine if you enter the collider, AND press E in the exact same frame.

I would try moving this into OnTriggerStay. The OnEnter only fires 1 time, when you first enter the collider, on trigger stay fires repeatedly as long as you stay in the collider.

This will continue to look for your keydown event each frame, and call the coroutine when you press E as long as you are still in the collider.

Hope this helps,
-Larry