Rotate around an object to its direction of velocity (C#)

Right now I am working on a 3D camera that is orbiting horizontally around the player. The player is a RigidBody rolling sphere. The player can freely rotate the axis horizontally but when there is no input I want the rotation to reset back to the direction of the velocity.

Right now all I need to know is how to situate the camera behind the player's direction of velocity by rotating the camera around the player.

Here is a crude drawing of what I am looking for:

Currently to update the camera to orbit around the player I use this script on the camera (with comments):

 using UnityEngine;
 using System.Collections;
 
 public class example : MonoBehaviour {
     
     public GameObject Player;
     //I assume you would use this PlayerRB to find data regarding the movement or velocity of the player.
     //public Rigidbody PlayerRB;
 
     private float moveHorizontalCamera;
     private Vector3 offset;
 
     // Use this for initialization
     void Start ()
     {   //the offset of the camera to the player
         offset = new Vector3(Player.transform.position.x - transform.position.x,  transform.position.y - Player.transform.position.y, transform.position.z - Player.transform.position.z);
     }
     
     // Update is called once per frame
     void Update ()
     {
         moveHorizontalCamera = Input.GetAxis("Joy X"); //"Joy X" is my right joystick moving left, none, or right resulting in -1, 0, or 1 respectively
 
         //Copied this part from the web, so I half understand what it does.
         offset = Quaternion.AngleAxis(moveHorizontalCamera, Vector3.up) * offset;
         transform.position = Player.transform.position + offset;
         transform.LookAt(Player.transform.position);
     }
 }
 

Any help at all would be great!