The random generated obstacles spawn outside the game platform

I'm making this game where a cube goes forward on a platform, and it has to dodge the obstacle (which are others cube) that are generated in a random way:

 public class BlockSpawner : MonoBehaviour
 {
     public Transform[] spawnPoints;
     public GameObject blockPrefab;
     public float timeBetweenWaves = 1f;
     private float timeToSpawn = 2f;
 
 
     // Update is called once per frame
     void Update()
     {
         if(Time.time >= timeToSpawn)
         {
             SpawnBlock();
             timeToSpawn = Time.time + timeBetweenWaves;
         }
     }
 
     void SpawnBlock()
     {
         int randomIndex = Random.Range(0, spawnPoints.Length);
 
         for (int i = 0; i < spawnPoints.Length; i++)
         {
             if (randomIndex != i)
             {
                 Instantiate(blockPrefab, spawnPoints[i].position, Quaternion.identity);
             }
         }
     }
 }

at the start, my problem was that the block spawners didn't move, so I made that the block spawners follow the player but 100z before it. Now the new problem is that the obstacle spawners change their X and fell off the platform, how do I fix their X position even when the player is moving right and left?