ignition problems, car starting then shutting down

Sometimes, when I start my car, it will idle for a few seconds, then immediately shut off. I mean shut the whole car down so nothing electrical can work. During this time I can't even get the key out.
So I restart the car and then everything is fine. But it just seems like sometime more than others that the starter has to work a little harder.The ignition part is really starting to worry me. I don't want to be stranded somewhere with my car having a faulty ignition.
** Car has 148k miles, and bought it at 140k miles.**  
I had a Ford Thunderbird that almost did the same thing, only I started loosing power to everything one at a time (i.e. one window, both windows, the radio, the a/c, etc.). And once I removed the steering column, it was the ignition switch and it was comming apart. I had to put the small B.B back into the hole, put the metal sliding track back into align, and put the plastic piece together with the housing)

Any help is appreciated, Thanks