As was already mentioned, there might be a problem with your joystick calibration. Normally, if your joystick is well-calibrated, FS will perceive that, when the joystick is in neutral stand, you are not applying back pressure or so.
However, if the joystick isn't calibrated, then, even when you're not touching the joystick, FS might think that you're applying back pressure and try to increase the aircraft's AOA and, for instance, takeoff.
Read your joystick's manual. You should be able to calibrate it using some sort of software that came with it. If that doesn't work, let us know. But, let's hope this works!
I had no problem at all calibrating my joystick (MS Sidewinder Pro). I connected the joystick, installed the software, and the joystick was allready well-calibrated.
Ivan Coninx - Brussels Aviation Photography