2002 Pontiac Grand Am

I have a 2002 Grand Am SE V6 with 87000 miles. I have never had any problems with it until the last few months. Sometimes it just randomly won't start. I had it towed 2 times and it started once it got to the mechanic. He looked it over and could not find anything wrong. The third time I had it towed and replaced the following: spark plugs, fuel pump, fixed a computer problem, crank sensor, cam sensor, EGR valve, and replaced the coolant container because the old one would not open. It worked fine for about a month and then the service engine light came on. I took it to two different people and they could not find anything wrong. The last time I had it checked on Saturday. It is now Tuesday and it won't start again. I have been the only owner and have made sure that all regular maintenance and tuneups have been performed. I am at a loss, what else could it be before I get ripped off anymore?
June 20, 2006.

The place I took it to had the car for 2 days. They checked all the previously replaced parts and could find nothing. No errors are showing up on the computer. On the first day they had it the car didn't start. On the second day it did. Luckily they didn't charge me anything. I really don't know what to do. Every time I leave for work I have to cross my fingers that it will start. I just wish someone could find the problem.

Jun 24, 2006.