Laggy behaviour after two object with colliders are generated on the same place

As the title says, I experience some really laggy behaviour after I Instantiate 2 objects on top of each other with 2D colliders and rigidbodies. I would have expected, that these 2 object would somehow repell each other and would not make contact after a little time, but they stay at the same place and cause fps drop. Is there any way to prevent this from happening (I generate these object randomly)? Or better, is there any way to achieve the behaviour I would have expected?