How to move 2D Object with WASD in Unity

You don't need those if statements. Just use += to append the input to the current transform position.

Move without Rigidbody:

public float speed = 100;
public Transform obj;

public void Update()
{
    float h = Input.GetAxis("Horizontal");
    float v = Input.GetAxis("Vertical");

    Vector3 tempVect = new Vector3(h, v, 0);
    tempVect = tempVect.normalized * speed * Time.deltaTime;

    obj.transform.position += tempVect;
}

Move Object with Rigidbody2D:

public float speed = 100;
public Rigidbody2D rb;

public void Update()
{
    float h = Input.GetAxis("Horizontal");
    float v = Input.GetAxis("Vertical");

    Vector3 tempVect = new Vector3(h, v, 0);
    tempVect = tempVect.normalized * speed * Time.deltaTime;
    rb.MovePosition(rb.transform.position + tempVect);
}

I suggest using the second code and moving the Rigidbody if you want to be able to detect collison later on.

Note:

You must assign the object to move to the obj slot in the Editor. If using the second code, assign the object with the Rigidbody2D to the rb slot in the Editor.

THIS CODE WORK 100% (you must try it.)

public float moveSpeed = 5;


void Start()
{
   
}


 void Update()
{

    if (Input.GetKey(KeyCode.D))
    {
        transform.position += Vector3.right * moveSpeed * Time.deltaTime;
        
    }
    else if (Input.GetKey(KeyCode.A))
    {
        transform.position += Vector3.right * -moveSpeed * Time.deltaTime;
        
    }

    else if (Input.GetKey(KeyCode.W))
    {
        transform.position += Vector3.up * moveSpeed * Time.deltaTime;

    }
    else if (Input.GetKey(KeyCode.S))
    {
        transform.position += Vector3.up * -moveSpeed * Time.deltaTime;

    }
}