Quaternion.Lerp rotate too soon

i use this code to rotate my avatar to targetPostion, but the problem is it alway rotate too soon & faster then the duration.

any ideas?

IEnumerator MoveToPosition(GameObject avatar, Vector3 targetPosition, float speed)
{
   // Rotate towards the target
   Vector3 direction = targetPosition - avatar.transform.position;
   Quaternion toRotation = Quaternion.LookRotation(direction);

   float STARmove = 0;
   float duration = 1;

   while (STARmove < duration)
   {

       STARmove += Time.deltaTime;


       // Calculate rotation based on interpolation ratio
       float t = Mathf.Clamp01(STARmove / duration);
       avatar.transform.rotation = Quaternion.Lerp(avatar.transform.rotation, toRotation, t);

       // Wait for a fixed time before next update
       yield return new WaitForSeconds(Time.deltaTime);
   }} 

>Solution :

Interpolate between the start and end rotations, not between the current and end rotations.