Random instantiation endlessly?

Something like this should do the trick.

 public List<GameObjects> objectsToSpawn;
 public float timeBetweenSpawns;
 public Transform spawnPoint;
 
 private float timer;
 
 void Start(){
     timer = timeBetweenSpawns;
 }
 
 void Update(){
     timer -= Time.deltaTime;
 
     if(timer < 0){
         timer = timeBetweenSpawns;
 
         SetNewSpawnPosition();
         
         int spawnIndex = Random.Range(0, objectsToSpawn.Count);
         Instantiate(objectsToSpawn[spawnIndex], spawnPoint.position, spawnPoint.Rotation);
     }
 }
 
 void SetNewSpawnPosition(){
     //Change the location of the spawn point however you want
 }

If you wanted to be super efficient here you could look into object pooling which is a great optimization for spawning objects like this, but this should serve as a good prototype script.