conserve momentum of vector3.moveTowards in 2D game

I have a character who is hanging in mid air with a gravitational force constantly pulling them downwards. however, when a mouse click is detected, the character accelerates towards the click. I have written the following code.

 public class controller : MonoBehaviour {
     private Vector3 target;
     Vector3 velocity = Vector3.zero;
     public Vector3 gravity;
 
     float startTime;
     float elapsedTime;
 
     bool gravOn = true;
     // Use this for initialization
     void Start () {
         startTime = Time.time;
     }
 
     // Update is called once per frame
     void FixedUpdate () {
 
         if (gravOn == true) {
             elapsedTime = Time.time - startTime;
             velocity += gravity * elapsedTime;
             transform.position += velocity * elapsedTime;
         }
 
         if ((Input.touchCount > 0 && Input.GetTouch (0).phase == TouchPhase.Began) || (Input.GetMouseButton (0))) {
 
             gravOn = false;
 
             target = Camera.main.ScreenToWorldPoint (Input.mousePosition);
             target.z = transform.position.z;
             transform.position = Vector3.MoveTowards (transform.position, target, 0.5f);
 
             startTime = Time.time;
 
         } else {
             gravOn = true;
         }
     }
 }

my problem is, when I release the mouse the character instantly stops accelerating towards the mouse click and instantly starts falling again. I would like the momentum of the acceleration caused by vector3.movetowards to be conserved, so the character could be "thrown" by the moveTowards function. What am i missing here?