In my experience, most cases of interior window icing are the result of one or more of the following car owner mistakes:
Using the recirculate function on the HVAC system
Failure to remove as much snow as possible from shoes before entering the car
Failure to remove wet floormats from the car in order to dry them
Keeping windows open, rather than using the HVAC system (on the A/C setting if necessary)
If none of these situations is applicable to you, then you may want to explore the possibility that the heater core is leaking. While this is not a strong probability on a car that is just a few years old, it is possible.