Getting ArgumentOutOfRangeException on array c#

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class PlayerInv : MonoBehaviour {
 
     //(CHANGE)
     //Gun AMMO (NOT FINAL PLEASE CHANGE TO MORE SPECIFIC NAMES TO CERTAIN GUN TYPES)
     public int AssaultA;
     public int SmgA;
     public int PistolA;
       public Vector2 scrollPosition;
     public List<string> Items;
     
     public Texture BackPack;
     public Texture gun;
     
     
     public int ArrayCounter;
     void Update(){
         
     }
     
     void OnGUI(){
         Rect rect = new Rect(0,0,800,600);
         
         GUI.DrawTexture(rect,BackPack);
         
         GUILayout.BeginArea(new Rect(40,100,200,400));
         scrollPosition = GUILayout.BeginScrollView(scrollPosition, GUILayout.Width(200), GUILayout.Height(500));
         foreach(string go in Items){
             
             GUILayout.Button(Items[ArrayCounter]);
             ArrayCounter++;
         }
         GUILayout.EndScrollView();
          GUILayout.EndArea ();
     }
 }

I keep getting this error

 ArgumentOutOfRangeException: Argument is out of range.
 Parameter name: index
 System.Collections.Generic.List`1[System.String].get_Item (Int32 index) (at /Applications/buildAgent/work/3df08680c6f85295/mcs/class/corlib/System.Collections.Generic/List.cs:633)
 PlayerInv.OnGUI () (at Assets/Scipts/PlayerInv.cs:33)