Trigger a scene with a timer

I have been looking for a timer that can trigger a scene when it hits 0 and there is no GUI please help
unity 5.5

A very easy (although not very robust) way to do this is the Invoke method.
Like this:

void OnTriggerEnter() // For example
{
  Invoke("ChangeScene", 10); // 10 seconds delay
}

void ChangeScene()
{
  SceneManager.LoadScene("Some scene");
}

You can improve this code a bit by using nameof:

void OnTriggerEnter() // For example
{
  Invoke(nameof(ChangeScene), 10); // 10 seconds delay
}

void ChangeScene()
{
  SceneManager.LoadScene("Some scene");
}

@ Diamonddoggames
Not sure if the answer above worked for you; but I use something closer to what you described. This is only a temporary feature that I intend to remove, but once certain scenes are loaded, a timer starts. When timer reaches 0, the scene auto switches back to the original scene. The way it was designed, the countdown displays on-screen, but you don’t have to do that.

Here is the code I use. I tried to strip out everything but the timer scripting.

public class Timer : MonoBehaviour 

{

	
    public string leveltoload;
    
            private float timer = 10f;

            private Text timerseconds;

	

            void Start () 
    
            {

                	    timerseconds = GetComponent<Text>();

            }


	
	void Update () 
    
                {
                   
        timer -= Time.deltaTime;

                           timerseconds.text = timer.ToString("f0");
 
                           if (timer <= 0)

                           {

   				     Invoke("LoadScene", 2.5f);

		           }
	
                  }



                void LoadScene()

                {

		         SceneManager.LoadScene("OLYMPUS");

	        }

}