IndexOutOfRangeException C#

Hey People,

Im pretty new to programming and ran into a problem while working on a script for a inventory system

IndexOutOfRangeException: Array index is out of range. Inventory.Update () (at Assets/_Scripts/Inventory.cs:57)

can anybody spot the problem in my code please?

 using UnityEngine;
 using System.Collections;
 
 public class Inventory : CollisionDetection {
     
     public GameObject[] InventoryArray;
     public int InventoryX;
     public float InventoryIncrease;
     public float[] targetPosition = new float[0];
     public float[] startPosition = new float[0];
     public GameObject inventory;
 
     //GameObject[] prefabArray;
     public GameObject prefab = null;
     public int amountToSpawn; //ARRAY.LENGTH
     static public int amountspawned = 0;
     public int x;
     public int a = 0;
     
     int xCounter = 0;
     int y;
     Vector3 newPos;
 
     public int pos;
     
     void Spawner (){
         for (int i = 0; i < amountToSpawn; i++) {
 
             newPos = transform.position;
             newPos.x = newPos.x + xCounter;
             newPos.y = newPos.y - y;
             
             xCounter = xCounter + 1;
             
             if(xCounter == x){
                 y += 1;
                 xCounter = 0;
             }
             
             (Instantiate (prefab, newPos, transform.rotation)as GameObject).transform.parent = inventory.transform;
             amountspawned ++;
         }
     }
 
     // Update is called once per frame
     void Update () {
     
         if (InventoryArray.Length >= amountspawned) {
             Spawner ();
         }
 
 
         InventoryArray = GameObject.FindGameObjectsWithTag("ItemInInventory");
         for ( int i=0; i < InventoryArray.Length; i++) {    
             print (InventoryArray [0].transform.position);
             InventoryArray[i].transform.localScale = new Vector3 (.7f,.7f,.7f);
             InventoryArray[a].transform.position = new Vector3(newPos.x,newPos.y,(inventory.transform.position.z)-.5f);
             GameObject.FindGameObjectWithTag("ItemInInventory").transform.parent = inventory.transform;
             a++;
             inventory.SetActive(false);
             inventory.SetActive(true);
         }
     }
 }