Random Spawn Help

I just can’t make script that will spawn enemy near player . The problem is because player is moving and if I set x and y position, he can leave that box. I tried with:

player.position = Vector3(10, 3, 10);
minimum.x = player.position.x - 10;
minimum.z = player.position.z - 10;
maximum.x = player.position.x + 10;
maximum.z = player.position.z + 10;

But it only get positions around player in certain frame. And when I want to spawn object:

transform.position = Vector3( Random.Range(minimum.x, maximum.x), transform.position.y, Random.Range(minimum.z, maximum.z) );

It spawns in that box, but player is not there.
How can I fix that? is there any easier way to this random spawn? I am beginner, still learning.

did you try something like
transform.position = Vector3( Random.Range(transform.position.x - 10,transform.position.x +10), transform.position.y,Random.Range( transform.position.z - 10,transform.position.z + 10)));