1 year old Trek 520 with mechanical disc brakes.
When I am pushing the bike around, both with and without loaded panniers, the front wheel frequently makes a low pitched "squealing" sound--almost a moan. With the front of the bike lifted off the ground, the wheel spins freely, with no apparent interference. There is no noise or any apparent problem. The noise appears to be accentuated when the wheel is not aligned with the bike--ie, turning left or right, but it can happen whether straight or turned.
The brakes seem to work fine.
There is no obvious sideways play in the wheel.
Since the brakes seem to work fine, and the noise doesn't happen when riding, I've been riding anyway--but I'm concerned that there might be some brake issue or something else I'm not thinking about.
What else should I be thinking about/checking?