How to Reset Quaternion/Rotation On 3D Object After Dragging Mouse?

Hello, I have an issue with resetting my gameobject's rotation. The rotation is based off mouse drag with restrictions. I have it to when the mouse is released the object returns to its starting rotation. But when I re-drag the object again the object rotation starts from where it was left off at from the previous drag. When I need it to drag from its starting rotation. I've tried many different methods nothing seems to work.

 public Camera cam;
 public float speed, minEulerX, maxEulerX, minEulerY, maxEulerY;
 float eulerX, eulerY, rotateY, rotateX, inputX, inputY;
 Quaternion startrot;
 bool touch;

 void Start()
 {
     startrot = transform.rotation;
 }

 void Update()
 {
     if (Input.GetMouseButtonDown(0))
     {
         Ray ray = cam.ScreenPointToRay(Input.mousePosition);
         if (Physics.Raycast(ray, out RaycastHit hit, Mathf.Infinity, Object))
         {
             inputX = Input.mousePosition.x;
             inputY = Input.mousePosition.y;
             touch = true;
         }
     }

     if (Input.GetMouseButton(0))
     {
         if (touch)
         {
             rotateX = -(Input.mousePosition.y - inputY) * speed;
             rotateY = -(Input.mousePosition.x - inputX) * speed;
             eulerX = Mathf.Clamp(eulerX + rotateX, minEulerX, maxEulerX);
             eulerY = Mathf.Clamp(eulerY + rotateY, minEulerY, maxEulerY);
             transform.rotation = Quaternion.Euler(-eulerX, eulerY, 0) * startrot;
             inputX = Input.mousePosition.x;
             inputY = Input.mousePosition.y;
         }
     }
 
     if (Input.GetMouseButtonUp(0))
     {
         transform.rotation = startrot;
         touch = false;
     }    
 }