Enemy wandering randomly in a certain range

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:

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class EnemyAI : MonoBehaviour {
5.  
6.     public float rotationSpeed;
7.     public float moveSpeed;
8.     public float maxSpeed;
9.     public float minRange;
10.     public float maxRange;
11.     public float moveRange;
12.     Animator anim;
13.     CharacterController controller;
14.  
15.     // Use this for initialization
16.     void Awake (){
17.         anim = GetComponent<Animator> ();
18.         controller = GetComponent<CharacterController> ();
19.     }
20.     void Start () {
21.     }
22.  
23.     // Update is called once per frame
24.     void FixedUpdate () {
25.         FollowPlayer ();
26.         StartCoroutine(MoveAround ());
27.     }
28.     void FollowPlayer(){
29.         Vector3 playerPos = GameObject.Find ("Player").transform.position;
30.         Vector3 lookDir = playerPos - transform.position;
31.         Vector3 moveDir = lookDir;// * moveSpeed;
32.         moveDir *= Time.fixedDeltaTime;
33.  
34.         if((Vector3.Distance(transform.position, playerPos) <= maxRange) && (Vector3.Distance(transform.position, playerPos) > minRange) ){
35.             Vector3 previous = transform.position;
36.             transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation (lookDir), rotationSpeed * Time.fixedDeltaTime);
37.             controller.Move(moveDir);
38.             float velocity = ((transform.position - previous).magnitude) / Time.fixedDeltaTime;
39.         //    Debug.Log("velocidad: " + velocity);
40.             previous = transform.position;
41.             anim.SetFloat ("speed", velocity);
42.         }
43.         if(Vector3.Distance(transform.position, playerPos) < minRange){
44.             controller.Move(Vector3.zero);
45.             Debug.LogWarning("hey");
46.             anim.SetFloat("speed",controller.velocity.magnitude);
47.         }
48.     }
49.     IEnumerator MoveAround(){
50.         Vector3 playerPos = GameObject.Find ("Player").transform.position;
51.         Vector3 randomPos = Random.onUnitSphere * moveRange;
52.         randomPos = new Vector3 (randomPos.x + transform.position.x, transform.position.y, randomPos.z + transform.position.z);
53.         Vector3 lookDir = randomPos - transform.position;
54.         Vector3 moveDir = lookDir;
55.         moveDir *= Time.fixedDeltaTime;
56.         Debug.Log ("Player Pos: " + playerPos);
57.         Debug.Log ("Random Pos: " + randomPos);
58.         Debug.Log ("Look Dir: " + lookDir);
59.         Debug.Log ("Move Dir: " + moveDir);
60.  
61.         if(Vector3.Distance(transform.position, playerPos) > maxRange){
62.             Debug.Log("Moving the enemy");
63.             Vector3 previous = transform.position;
64.             transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation (lookDir), rotationSpeed * Time.fixedDeltaTime);
65.             controller.Move(moveDir);
66.             float velocity = ((transform.position - previous).magnitude) / Time.fixedDeltaTime;
67.         //    Debug.Log("velocidad: " + velocity);
68.             previous = transform.position;
69.             anim.SetFloat ("speed", velocity);
70.             Debug.Log("Enemy moved");
71.             yield return new WaitForSeconds(2f);
72.             Debug.Log("esperando primeros 2 segundos");
73.         }
74.         Debug.Log ("he llegado al destino");
75.         yield return new WaitForSeconds(2f);
76.         Debug.Log ("COroutine final");
77.     }
78.  
79.     void OnDrawGizmosSelected(){
80.         Gizmos.color = Color.green;
81.         Gizmos.DrawWireSphere (transform.position, maxRange);
82.         Gizmos.DrawWireSphere (transform.position, minRange);
83.     }
84. }
85.