Rotate an object using Quaternion.RotateTowards() inside a Coroutine?

Hello, i am trying to rotate an object inside a Coroutine using Quaternion.RotateTowards(). But its not rotating smoothly like it does in Update(). instead, it snaps to the target rotation. What is wrong? This is my script:

 public class SpinWheelScript : MonoBehaviour {

 public GameObject[] rewards;
 public GameObject[] pointerDir;
 public GameObject[] ringDir;
 public GameObject pointer;
 public GameObject ring;

 private Quaternion pointerTargetRotation;
 private Quaternion ringTargetRotation;

 private bool spinIsEnabled = true;
 private bool isSpinning = false;

 private float pSpeed;
 private float rSpeed;
 private float pointerRotateFloat;
 private float ringRotateFloat;

 private int rewardEnabler = 0;
 private int randomReward;
 private int pRandomDir;
 private int rRandomDir;
 private int plastRandomDir = 0;
 private int rlastRandomDir = 0;

 private void Update()
 {
     if (spinIsEnabled == false)
     {
         // Do Nothing
     }

     else if (spinIsEnabled == true && isSpinning == false)
     {
         // Select reward
         if (rewardEnabler == 0)
         {
             RewardSelector();
             rewardEnabler = 1;
         }
         StartCoroutine(Spin());
     }
 }


 IEnumerator Spin()
 {
     isSpinning = true;
     pSpeed = 0;
     rSpeed = 0;

     // Speed increasing spin for 5 seconds

     PointerRandomDirection();
     RingRandomDirection();

     while (true)
     {
         pointerRotateFloat = (((pRandomDir + 1) * 60) - 30) - pointer.transform.rotation.z;
         ringRotateFloat = (((rRandomDir + 1) * 60) - 30) - ring.transform.rotation.z;

         pSpeed = (pointerRotateFloat / 2);
         rSpeed = (ringRotateFloat / 2);

         pointerTargetRotation = Quaternion.Euler(new Vector3(0, 0, pointerRotateFloat));
         pointer.transform.rotation = Quaternion.RotateTowards(pointer.transform.rotation, pointerTargetRotation, pSpeed * Time.deltaTime);
         ringTargetRotation = Quaternion.Euler(new Vector3(0, 0, ringRotateFloat));
         ring.transform.rotation = Quaternion.RotateTowards(ring.transform.rotation, ringTargetRotation, rSpeed * Time.deltaTime);

         if ((pointer.transform.rotation == pointerTargetRotation) && (ring.transform.rotation == ringTargetRotation))
             break;
     }

     yield return new WaitForSeconds(1);

     Debug.Log("Done!");
 }

 private int RewardSelector()
 {
     randomReward = Random.Range(0, rewards.Length);

     return randomReward;
 }

 private int PointerRandomDirection()
 {
     int pRandomDir = plastRandomDir;

     if (pointerDir.Length <= 1)
         return 0;

     while (pRandomDir == plastRandomDir)
     {
         pRandomDir = Random.Range(0, pointerDir.Length);
     }

     plastRandomDir = pRandomDir;
     return pRandomDir;
 }

 private int RingRandomDirection()
 {
     int rRandomDir = rlastRandomDir;

     if (ringDir.Length <= 1)
         return 0;

     while (rRandomDir == rlastRandomDir)
     {
         rRandomDir = Random.Range(0, ringDir.Length);
     }

     rlastRandomDir = rRandomDir;
     return rRandomDir;
 }
 }

Thanks in advance :)