Move Enemy randomly in a range. 3D

Hi: Im working on a FPS mixed with some survival in 3D. I have an animated model that represents my enemy. I can make him move towards me if I am in range. If he gets closer enough he stops moving(and animating). Now Im trying to achieve a Wandering behaviour.

My idea goes like this: The enemy starts in the start position. He checks if the player is in range, if true then FollowPlayer() if false then MoveAround(), this means that he calculate a random position in a certain range of his actual position, Slerp to it and then move to that random position. After reaching the random position he should wait X seconds until the next move . The MoveAround() method I have is a Coroutine but I cant make it work. Here is the script: using UnityEngine; using System.Collections;

 public class EnemyAI : MonoBehaviour {
 
     public float rotationSpeed;
     public float moveSpeed;
     public float maxSpeed;
     public float minRange;
     public float maxRange;
     public float moveRange;
     Animator anim;
     CharacterController controller;
 
     // Use this for initialization
     void Awake (){
         anim = GetComponent<Animator> ();
         controller = GetComponent<CharacterController> ();
     }
     void Start () {
     }
     
     // Update is called once per frame
     void FixedUpdate () {
         FollowPlayer ();
         StartCoroutine(MoveAround ());
     }
     void FollowPlayer(){
         Vector3 playerPos = GameObject.Find ("Player").transform.position;
         Vector3 lookDir = playerPos - transform.position;
         Vector3 moveDir = lookDir;// * moveSpeed;
         moveDir *= Time.fixedDeltaTime;
 
         if((Vector3.Distance(transform.position, playerPos) <= maxRange) && (Vector3.Distance(transform.position, playerPos) > minRange) ){
             Vector3 previous = transform.position;
             transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation (lookDir), rotationSpeed * Time.fixedDeltaTime);
             controller.Move(moveDir);
             float velocity = ((transform.position - previous).magnitude) / Time.fixedDeltaTime;
         //    Debug.Log("velocidad: " + velocity);
             previous = transform.position;
             anim.SetFloat ("speed", velocity);
         }
         if(Vector3.Distance(transform.position, playerPos) < minRange){
             controller.Move(Vector3.zero);
             Debug.LogWarning("hey");
             anim.SetFloat("speed",controller.velocity.magnitude);
         }
     }
     IEnumerator MoveAround(){
         Vector3 playerPos = GameObject.Find ("Player").transform.position;
         Vector3 randomPos = Random.onUnitSphere * moveRange;
         randomPos = new Vector3 (randomPos.x + transform.position.x, transform.position.y, randomPos.z + transform.position.z);
         Vector3 lookDir = randomPos - transform.position;
         Vector3 moveDir = lookDir;
         moveDir *= Time.fixedDeltaTime;
         Debug.Log ("Random Pos: " + randomPos);
         Debug.Log ("Look Dir: " + lookDir);
         Debug.Log ("Move Dir: " + moveDir);
 
         if(Vector3.Distance(transform.position, playerPos) > maxRange){
             Debug.Log("Moving the enemy");
             Vector3 previous = transform.position;
             transform.rotation  = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation (lookDir), rotationSpeed * Time.fixedDeltaTime);
         controller.Move(moveDir);
         float velocity = ((transform.position - previous).magnitude) / Time.fixedDeltaTime;
     //    Debug.Log("velocidad: " + velocity);
         previous = transform.position;
         anim.SetFloat ("speed", velocity);
         Debug.Log("Enemy moved");
         yield return new WaitForSeconds(2f);
         Debug.Log("esperando primeros 2 segundos");
     }
     Debug.Log ("he llegado al destino");
     yield return new WaitForSeconds(2f);
     Debug.Log ("COroutine final");
 }

 void OnDrawGizmosSelected(){
     Gizmos.color = Color.green;
     Gizmos.DrawWireSphere (transform.position, maxRange);
     Gizmos.DrawWireSphere (transform.position, minRange);
 }

}