Can I emulate simple space-like gravity?

Hey! I have this script here, for a 2D side scrolling game. It is attached to my player object.

 using UnityEngine;
 using System.Collections;
 
 public class Movement : MonoBehaviour {    
 
     //Variables
     public float PlayerSpeed = 5f;
     public float PlayerRotation = 10f;
     public float JumpForce = 800f;
     public bool IsRight = false;
     public bool CanFlip = true;
 
     //Update Function
     void Update () {
                 //Move
                 float Move = Input.GetAxis ("Horizontal");
                 float MoveVertical = Input.GetAxis ("Vertical");
 
                 rigidbody2D.velocity = new Vector2 (MoveVertical * PlayerSpeed, rigidbody2D.velocity.x);
                 rigidbody2D.velocity = new Vector2 (Move * PlayerSpeed, rigidbody2D.velocity.x);
                 rigidbody2D.AddTorque (Move * PlayerRotation);
                 rigidbody2D.AddTorque (MoveVertical * PlayerRotation);
                 
                 //Flip
                 if (Move > 0 && !IsRight) {
                         Flip ();
                 } else if (Move < 0 && IsRight) {
                         Flip ();
                 }
                 
                 //Jump
 //                if (Input.GetKeyDown (KeyCode.W)) {
 //                    rigidbody2D.AddForce(new Vector2 (0, JumpForce));
 //                }
         }
 
     //Flip Function
     void Flip() {
         if (CanFlip) {
                         IsRight = !IsRight;
                         Vector3 Scale = transform.localScale;
                         Scale.x *= -1;
                         transform.localScale = Scale;
                 }
     }
 }

It works perfectly! I am able to move my character in all four directions, and a slight torque is applied. What I want to achieve is a way to make the gravity feel a little more floaty, like space. Even when he is not moving I would love to see a slight 'bobbing' around. Is there a fairly simple way to do this?