Proper way to move Rigidbody GameObject

You move Rigidbody with Rigidbody.MovePosition and rotate it with Rigidbody.MoveRotation if you want it to properly collide with Objects around it. Rigidbody should not be moved by their position, rotation or the Translate variables/function.

The "w" is not predefined like SherinBinu mentioned but that's not the only problem. If you define it and use KeyCode.W it still won't work. The object will move once and stop.

Change

Vector3 move = new Vector3(0, 0, 1) * speed;
rb.MovePosition(move);

to

tempVect = tempVect.normalized * speed * Time.deltaTime;
rb.MovePosition(transform.position + tempVect);

This should do it:

public float speed;
private Rigidbody rb;


public void Start()
{
    rb = GetComponent<Rigidbody>();
}

public void Update()
{
    bool w = Input.GetKey(KeyCode.W);

    if (w)
    {
        Vector3 tempVect = new Vector3(0, 0, 1);
        tempVect = tempVect.normalized * speed * Time.deltaTime;
        rb.MovePosition(transform.position + tempVect);
    }
}

Finally, I think you want to move your object with wasd key. If that's the case then use Input.GetAxisRaw or Input.GetAxis.

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

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

"w" is not predefined unless you explicitly define it. Use KeyCode.W