Whenever I’ve encountered this type of sound it has usually proven to be caused by the plastic shrouding around the steering column, possibly some part of it rubbing on the steering wheel or steering shaft.
See if placing a hand on the shroud, below or above the column, just behind the steering wheel, helps to quiet the sound.
Another place that the sound can be generated from is a rubber boot around the steering shaft itself at the front floor location.
Since you only hear it while parked or at low speed then it must be fairly faint. Road noise probably makes the sound seem inaudible.
It’s probably nothing serious, but try and figure out where it’s originating, if possible, and discuss it when the car goes into the dealer for the next service visit.