Why has my 2014 Camry SE 2.5L Automatic Transmission shifting into manual first?

Your car 'thinks' it is being told to go to manual 1, so it does it. The problem is going to exist in the switch that the driver presses to downshift manually, transmission control unit (TCM), or wiring between the two. I would first check to make sure there isn't some sort of beverage spilled under the shifter.