What logic should i implement in this 2D game?

Hello everyone, I would like to ask about a game i am making,it is a about a 2D game where the player goes from up to down, and there are obstacles being generated randomly while the background(which is the movable object) moves up. My question is: what logic should i implement in regard for obstacle generation?My current implementation (which is wrong) is creating a queue holding the objects and then comparing the position of the item on peek of the queue with the distance of the player and then creating a new object,but this implementation keeps generating objects non-stop and this ruin the game,So how should i think about that. Till now this is my code regarding the obstacles: using System.Collections; using System.Collections.Generic; using UnityEngine;

 public class ObstacleManager : MonoBehaviour {
     public float scrollSpeed;
     public int numberOfObjects;
     public float recycleOffset;
 
     public Transform prefab;
     public Vector3 minSize, maxSize, minGap, maxGap;
     public float minY, maxY;
 
 
     private static Vector3 startPos;
     private Vector3 nextPosition;
     private Queue<Transform> objectQueue;
 
 
     // Use this for initialization
     void Start () {
         GameEventManager.GameStart += GameStart;
         GameEventManager.GameOver += GameOver;
         objectQueue = new Queue<Transform>(numberOfObjects);
         enabled = false;
     }
     
     // Update is called once per frame
     void Update ()
     {
 //        if (objectQueue.Count > 0 && prefab != null) {
 ////            Debug.Log("1: "+objectQueue.Peek().localPosition.y + recycleOffset);
 ////            Debug.Log("2: "+-(PlayerController.distanceTraveled));
 ////            Debug.Log(objectQueue.Peek().localPosition.y + recycleOffset < -(PlayerController.distanceTraveled));
 //        if(objectQueue.Peek().localPosition.y + recycleOffset < -(PlayerController.distanceTraveled)){
 //            Recycle();
 ////            Debug.Log(prefab.position);
 //            }
 //        }
 
 
     }
 
 
     public void ObsctaclesMovement (float speed)
     {
         float newPos = Mathf.Repeat(Time.time * speed,10);
         transform.position = startPos + Vector3.up * newPos;
     }
 
     private void GameStart () {
         nextPosition = startPos;
         for (int i = 0; i < numberOfObjects; i++) {
             objectQueue.Enqueue((Transform)Instantiate(
                 prefab, new Vector3(prefab.position.x, 0f, 0f), Quaternion.identity));
         }
         for(int i = 0; i < numberOfObjects; i++){
             Recycle();
         }
         enabled = true;
     }
 
     private void GameOver () {
         enabled = false;
     }
 
     private void Recycle () {
         Vector3 position = nextPosition;
         Vector3 scale = new Vector3(
             Random.Range(0.5f, 6.5f),
             Random.Range(-1.5f, -16f),
             0f);
         position.x = scale.x;
         position.y = scale.y;
 
         Transform o = objectQueue.Dequeue();
         o.localPosition = position;
 
         objectQueue.Enqueue(o);
 
         nextPosition = new Vector3(
             Random.Range(0.5f, 6.5f),
             Random.Range(-1.5f, -16f) ,
             0f);
 //            Debug.Log("nex position: "+nextPosition);
 
 
     }
 }