How to Rotate Game Object in specific Angle repeatedly on Key Press?

Man thanks @Casy10 a ton it is rotating as I wanted it to :) , one thing i want to implement is the triangle is rotating fine but is there a way to see its rotation smoothly like i want the user to see the triangle rotate +120 or -120 degrees. thanks again :)

@manikiran22 This will do what you want nicely, I think.

 using UnityEngine;
 using System.Collections;
 
 public class FixedAngleRotator : MonoBehaviour
 {
     public Vector3 EulerRotation = new Vector3(0f, 120f, 0f);
     public float TimeToRotate = .5f;
 
     private bool rotating;
 
     private void Update()
     {
         if (!rotating)
         {
             if (Input.GetKeyDown(KeyCode.W))
             {
                 StartCoroutine(doRotate(EulerRotation));
             }
             else if (Input.GetKeyDown(KeyCode.S))
             {
                 StartCoroutine(doRotate(-EulerRotation));
             }
         }
     }
 
     private IEnumerator doRotate(Vector3 rotation)
     {
         Quaternion start = transform.rotation;
         Quaternion destination = start * Quaternion.Euler(rotation);
         float startTime = Time.time;
         float percentComplete = 0f;
         rotating = true;
         while(percentComplete <= 1.0f)
         {
             percentComplete = (Time.time - startTime) / TimeToRotate;            
             transform.rotation = Quaternion.Slerp(start, destination, percentComplete);
             yield return null;
         }
         rotating = false;
     }
 
 }