Only starts in neutral

Could only start the 1994 Olds Bravada in Neutral. Happened only once. It's been three days since it happened. In Park it sounded like it would sound at the beginning of the battery getting ready to go dead and the vehicle not starting. All the regular noises, eg., seat belt noise, etc, are emitted when trying to start it in Park. I then wiggled the shifter to no avail. Then I put it in Neutral, got that sort of giddy-up ya get when it doesn't want to start, like a hitch, (hard to explain) and then it started. Not right a way. But after about three tries. Then it never happened again. AND, now when I start it in Park, sometimes you hear that "click? tick, tick, tick," noise you get sometimes when your battery is actually dead. ??????Starter issue?

Update: While in Park and Neutral, turning the key in the ignition all the way will not start it, BUT if I turn the key just a hair, it will start, and I mean just a hair. And it actually doesn't sound like the battery going dead anymore. It sounds like a regular start. This seems to happen more often when I have started the car and let it run for about only a minute and then shut it off. If I let it run longer it seems to start right up.

Most chain type auto parts stores will check your battery for free.

My Dodge diesel showed a check engine light- P0137/low MAP sensor input voltage and was just a little harder than normal although my volt-ohm meter showed 12.57 volts.
A load test showed it bad.
After installing a new battery, the engine started like old times, the check engine light went out and the P0137 went away.