If you unlock the car with it in Park and leave it running, the car will automatically lock again. It doesn't always happen, has happened a few times where I was locked out of the car. I've learned to leave the window down or leave the door open when I step out. Any idea on what to look at to fix this?

I get the same thing on my 96 Achieva. Did you have any kind of after market security or keyless remote installed??