96 crown Vic starts fine on flat ground but when on incline won’t start.

Hello, this is a "no crank" situation? You turn the key and it will not crank, but you use a screwdriver and jump it? I would be looking at electrical connections and ensure all cables and connections are secure and free of corrosion. Other than that, hands on testing from a local professional is required.

Park vehicle on FLAT GROUND !