How do i get the cube to turn when up and right or left arrow is pressed?

Right now, the cube is moving up, down, left and right but it doesnt turn as its moving in the direction its going.

I want the cube to turn when its moving in the direction its heading towards.

the cube is on another cube that is flat and larger on the Y axis, so only X and Z are free.

Replace your Move() with this:

void Move()
{
	Vector3 v3 = new Vector3(SnakeSpeed * Time.deltaTime *Input.GetAxis("Horizontal"),0,SnakeSpeed * Time.deltaTime *Input.GetAxis("Vertical"));
	transform.Translate(v3, Space.World);
	if (v3 != Vector3.zero)
		transform.rotation = Quaternion.LookRotation(v3);
}