How to smoothly move player in circular shape around a point??

Currently I am using this code to move player in circular motion.

float x = CrossPlatformInputManager.GetAxis("Horizontal") * Time.deltaTime * speed;
transform.RotateAround(pivot.position, new Vector3(0,0,1), x);     

everything is working fine but when I putt off hands from controls, it still moves slowly. to stop that I have to press opposite button. and first it stops and again I have to press the button to move it reverse… Sorry I am absolute beginner to unity…

try this:

    float x = speed * 5 * Input.GetAxis("Horizontal");
    transform.Rotate(0, x, 0);

you will need to make a float speed