2002 Grand Am starts sometimes

My Grand Am SE, 2.2L automatic has about 50K miles on it. Serviced recently. 2 times in the last 6 weeks it hasn't started. The starter cranks, plenty of battery. I tried for about an hour before giving up. Occassionally when I was trying to start it, it sounded like it was going to catch, but instead of the engine catching, I heard a whirring sound like a motor spinning down. I think that was the starter motor.

The first time it wouldn't start, I tried again next morning but still no luck. The tow truck guy came, tried to start it, and it started right up. No problem with it for the next 3 weeks, then it won't start gain. This time I have it towed to a garage, but it's the end of the day and they are closed so no one can look at it. The mechanic looks at it the next morning, and it starts right up.

Any ideas?

What did you hav serviced?

Crank shaft position sensor, or your ignition systems(coils) got a short. But it could be something more simple like a fuel filters pluged. A loose gas cap...
All of these can be checked out first, so you or someone else ,wont just go throwing parts at it till its fixed.

It had the manufacturer's standard 50K service: oil, cooling system, transmission, and a 24 pt inspection. I hope they checked the fuel filter but the invoice doesn't say specifically. I'll check it and the fuel cap. Thanks for the help!