Wrong contineous rotation to car

In my 2d game, I want to rotate car face based on collision detected. But at present after 3 to 4 collision its doing continuous rotation only rather than moving straight after collision.

Here is my straight movement related code:

 myRigidbody.MovePosition (transform.position + transform.up * Time.deltaTime * GameManager.Instance.VehicleFreeMovingSpeed);

For better collision purpose, I have used Rigidbody position change approach.

Here is my collision time code:

 public void OnCollisionEnter2D (Collision2D other)
     {
         if (other.gameObject.CompareTag (GameConstants.TAG_BOUNDARY)) {
             ContactPoint2D contact;
             contact = other.contacts [0];
             Vector3 reflectedVelocity = Vector3.Reflect (transform.up, contact.normal);
             direction = reflectedVelocity;
         } 
     }

  if (direction != Vector3.zero && pathGenerator.positionList.Count <= 0) {
     float angle = Mathf.Atan2 (direction.y, direction.x) * Mathf.Rad2Deg;
     Quaternion targetRot = Quaternion.AngleAxis (angle - 90f, Vector3.forward);
     transform.rotation = Quaternion.Slerp (transform.rotation, targetRot, 0.1f);

     if (Quaternion.Angle (transform.rotation, targetRot) < 5f) {
         transform.rotation = targetRot;
         direction = Vector3.zero;
     }

 }

Rotation get applied within other code so that car was changing its face correctly and that method not affecting here that I have checked by placing debug statement.

Share you side thought for this.