With the VW’s I’ve owned over the years, the default position has been;
unlock the car but don’t open any of the doors; car will automatically re-lock itself after a short predetermined time period (sorry, can’t remember off what that predetermined period is).
unlock the car and then open and close one of the doors; the car will not automatically lock itself again, and it is necessary to lock it in the normal way - either pressing the lock button on the key fob or if the car’s keyless, touching the sensor on one of the front doors.
Thanks everyone. I thought it should lock after a while if I got out of the car and forgot to lock it with the key fob and then moved the fob out of range.