Look rotation viewing vector is zero

[hasty bluff]

this message start logging into my console when the player is idle when I added "Slerp" to make the player face the direction it is moving

float rotateSpeed = 10f;

        transform.forward = Vector3.Slerp(transform.forward, moveDir, Time.deltaTime * rotateSpeed);

[civic parrot]

Its because moveDir is a zero vector when that message is displayed

wrap your slerp call with something like:

if (moveDir != Vector3.zero) 
{

}

Slerping to a zero vector doesnt make sense, so it puts this in the console to give a heads up