bot AI half working

hi all, i've made this simple script for a walking bot, but i don't know why, sometimes it simply crashes and the gameobject stops moving or doing anything.

here's the script using UnityEngine; using System.Collections;

 public class EnemyMoving : MonoBehaviour {
 
     public GameObject player;
     public int temp;
     public float turnTemp;
     public float distanceTemp;
     public Vector3 translation;
     public GameObject target; 
     public float distance;
     public float maxDistance = 20f;
     public float minDistance = 5.0f;
     private bool isWalking = false;
     private bool isRotating = false;
     private float startPointX;
     private float startPointY;
     private float startPointZ;
     private float time0;
     public float waitTime;
     private bool firstTimeWait = true;
     public Quaternion targetRotation;
     public Vector3 tempVector3;
     private enum states
     {
         NONE,
         WAIT,
         TURN,
         AHEAD
     }
     private states currentState;
 
     void Start () 
     {
         player = GameObject.FindGameObjectWithTag("Player");
     }
     
 
     void Update () 
     {
         if (currentState == states.AHEAD)
         {
             GoAhead();
         }
         else if (currentState == states.TURN)
         {
             turn();
         }
         else if (currentState == states.WAIT)
         {
             Wait();
         }
         else if (currentState == states.NONE)
         {
             FirstLevelRandom();
         }
     }
 
     void FirstLevelRandom()
     {
         temp = Random.Range(0,3);
         switch(temp)
         {
         case 1:
             currentState = states.WAIT;
             Debug.Log("wait");
             break;
         case 2:
             currentState = states.TURN;
             Debug.Log("turn");
             break;
         case 3:
             currentState = states.AHEAD;
             Debug.Log("ahead");
             break;
         }
     }
 
     void Wait() 
     {
         if (firstTimeWait)
         {
             waitTime = Random.Range(2,8);
             firstTimeWait = false;
             time0 = Time.time;
         }
         else
         {
             float time1 = Time.time;
             if (time1 - time0 >= waitTime)
             {
                 currentState = states.NONE;
                 firstTimeWait = true;
             }
         }
     }
 
     void turn()
     {
         if (!isRotating)
         {
             turnTemp = Random.Range(0, 360);
             isRotating = true;
             targetRotation = Quaternion.Euler(0, turnTemp, 0);
         }
         else 
         {
             if (transform.rotation.y != targetRotation.y)
             {
                 transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, 100f);
             }
             else 
             {
                 currentState = states.NONE;
                 isRotating = false;
             }
         }
     }
 
     void GoAhead()
     {
         if (!isWalking)
         {
             startPointX = transform.position.x;
             startPointY = transform.position.y;
             startPointZ = transform.position.z;
             distanceTemp = Random.Range(10, 50);
             tempVector3 = new Vector3 (startPointX, startPointY, startPointZ + distanceTemp); 
         }
         else
         {
             if (transform.position != tempVector3)
             {
                 transform.Translate(Vector3.forward * Time.deltaTime * 10);
             }
             else
             {
                 currentState = states.NONE;
                 isWalking = false;
             }
         }
     }
 
     void FollowPlayer()
     {
         transform.LookAt(player.transform);
         transform.Translate(Vector3.forward * Time.deltaTime);
     }
 }
 

i know that the code is not optimized at all, can anyone find the bug here?? thank you very much!!