Instantiated Object spawning at wrong position

I'm trying to make an object/objects instantiate when OnTriggerEnter is activated.

At first this worked fine, the objects appeared when the trigger was entered just as needed.

Original script-

 using UnityEngine;
 using System.Collections;
 
 public class HazzardSpawner : MonoBehaviour
 {
 
     public GameObject hazzardType;
 
     void OnTriggerEnter()
     {
         Instantiate (hazzardType, transform.position, transform.rotation);
         Destroy(gameObject);
 
             }
 }
 

Now I get a little more technical and want to add a variation along the x axis to where they spawn.

new script- using UnityEngine; using System.Collections;

 public class HazzardSpawner : MonoBehaviour
 {
 
     public GameObject hazzardType;
     public int spawnVariation;
 
     void OnTriggerEnter()
     {
         Vector3 spawnPosition = new Vector3 (Random.Range (-spawnVariation, spawnVariation), 0, 0);
         Instantiate (hazzardType, spawnPosition, transform.rotation);
     }
 }
 

It adds the variation along the x axis, but for some reason its also affecting where the objects spawn along the z axis. Every time its spawning the objects about 20 units away from the origin point on the Z axis.

???

This is the trigger(highlighted) and its origin point.

I've added this sphere to show where the objects are now spawning from(y axis)