Erratic climate control

Hi,

Had my climate control on "vent" only set at 60 degrees. (Not in automatic mode, not in recirculate mode, not in a/c mode, just on fan setting only)
Had fan on medium speed.

For about an 1 hour drive, total. Fan occasionally went to high blower speed at least twice and also went from blowing the 60 degree outside air to 90 degree heated air.

Shut off climate control, waited about 5 minutes, (still driving) and when I put it back on, it was at 90 degrees. Lowered it back to 60 degrees and it was fine for the rest of the trip.

I did not accidentally press the steering wheel controls, it just happened on its own.

Thank you for the advice.