Spawn game objects randomly with no overlapping

Hey! So i am making a new game wich requires me to spawn game objects on start. The randon spawning is not the problem, the problem is the reprtition of the randomly generated x and z positions. I am trying to spawn them as an array and then check the position of each object with respect to the one instantiated before it and if it is same just change the z posiotion si that they come one after the other.

Below is the code

 while(i<10)//obstacle instantiating from time 1nd time ground instantiating
     {

         obstacleClone2[i] = (GameObject)Instantiate(obstacle2);
         //every time previous ground position "z".
         obstacleClone2[i].transform.parent = mapSectionTwo.transform;
         obstaclePosition2 = new Vector3(Random.Range(-3, 4), 1, Random.Range(mapSectionTwo.transform.position .z-20, mapSectionTwo.transform.position .z+70));

        if((obstaclePosition2.x == -3) || (obstaclePosition2.x == 0) || (obstaclePosition2.x == 3))
         {
             obstacleClone2[i].transform.position =obstaclePosition2; 
             //Debug.Log(obstacleClone2[i].transform.position);

                if((i!=0)&&(obstacleClone2[i].transform.position==obstacleClone2[i-1].transform.position))
                {
             //Debug.Log ("same Position2");
             obstacleClone2[i].transform.position=obstacleClone2[i].transform.position + new Vector3(0, 0, 10);
                 
            }

         }
         
         i++;
         
     }

Even though this function is called once int he start, it soud go through the loop, correct??

Can somebody help me??Thanks in advance.