How are you shutting down the AC?
There are two ways to 'turn off the AC' with the automatic climate control.
- Press the ECO button (A/C OFF on 08+ models). This simply turns off the A/C compressor and breaks the auto cycle.
- Press the fan speed down all the way, then press it one more time. This turns the Auto Climate control off for good. If you are doing this, it should not come back on when you restart the car until you reactivate it by pressing 'Auto' of any other button.
At first read, it sounds like you have knocked it out of automatic mode. If it is in automatic mode, it would automatically wait for few minutes when you restart.
My suggestion, stop turning the A/C off before turing the car off, or use method 2.