insert the key, turn to position 1, all dash lights will come on, but don't proceed to start the car. Once the nuissance seat belt buzzer stops, and ensuring the radio and climate control fan are all the way off, apply and release the the brake pedal, listening for the mechanism that allows you to shift from park to engage. If you have intermittency here I would start by checkin the the brake switch, down by the pedal to see if it is not aligned or has suffered some sort of damage. If you hear the shift release mechanism engage appropriately then I would move onto cleaning the shift release button, as mentioned above it does get gummed up.

Good luck getting this sorted, keep us updated!