2003 Chevrolet Trailblazer LS. Warning lights: service engine soon sometimes. Question = when i drive for awhile and then stop like shopping when i go to start it, it acts like its flooded and it takes a few time to get started and when it does it shutters for a bit then evens out. I've had it on the engine test thing and they told me that it was the serpentine belt and thermostat which i dont think that has anything to do with how it acts.
Answer: Your check engine light can come on if you have a bad thermostat, and that also causes Driveability issues. When the engine computer can't tell what temperature the vehicle is running at, it defaults in a set fuel/air ratio to prevent damage from overheating. This can seem like it's running poorly and would cause a hard starting condition.
Assuming you don't have any other trouble codes, you should at least get the thermostat replaced and a new belt if they said it was bad. Otherwise, from what you describe, you could have a clogged air filter, carbon build up in the throttle body, clogged fuel filter or injectors that could be causing your hard start and rough running. Best to get checked out fully by a trained technician.