How to smooth my camera (Vector3.Lerp)

Im trying to make a racing game and I want the camera to follow my car smoothly and to look at a certain point smoothly with Lerp and Slerp. But it kinda lag and looks like the camera go forward every seconds and it's not smooth at all...

  to = cible.transform.position -

cam.transform.position; cam.transform.rotation = Quaternion.Slerp(cam.transform.rotation, Quaternion.LookRotation(to), 6 Time.smoothDeltaTime); cam.transform.position = Vector3.Lerp(cam.transform.position, posini.transform.position, 15 Time.smoothDeltaTime);

Thanks for any advice