Car will not start

Four cylinder automatic

Hi. Recently (within the past six months or so) the car will immediately start only intermittently. Other times you will hear a click and the engine whirring, almost as though you have a drained battery, but the interior lights come on, radio comes on, etc. You have to push the gear shift around while it is in the park position and then it will start (sometimes you have to lock the wheel, and then push the shifter around in the park position a few times for it to start). It seems as though the car is not registering that it is in park, and therefore it will not start. Could it be something else entirely? If it is just a sensor issue, is the repair simple enough that we would be able to do it yourself?
Thank you.