2006 Chrysler 300 2.7L

I was in the Army when my wife bought this car.
She had problems with it turning off on her before.
She left it in Florida while we were at Ft. Drum, NY.
It sat for a year and a half. The batter was just
replaced prior to her leaving. When I came home, it
would start and run just fine. I went to replace the
tires and it would still run like normal. I drove for a
bout 15 minutes and pulled into a mechanic shop
to have it checked out. It shut off on me when I put
it in Park. Replaced the starter and now it won't
even turn over. The battery is still good, the
connectors are clean, and so are the relays. What
might be my problem? Everything works. It just
won't turn over and start.