A couple of days ago while waiting in a drive thru line my 05 Trailblazer randomly started to shake while Idle (the A/C was on) and the car shutoff seconds later.
I recently just replaced all the spark plugs as well as all coils and the problem still persists. In addition, I have noticed that the car smells of gas when starting up.
I have had this issue before and the car would shut off as soon as the A/C would be turned on (This was fixed with a simple cleaning of the Throttle Body).
At the moment I am able to run the car with A/C and not have it shut off. No CEL is on and I would appreciate any help.

 

Have you scanned for any current/pending/history codes?

Since you mention the smell of gasoline when you start up, I would check the fuel pressure regulator for leaks and proper operation, and also look at the EVAP purge valve solenoid that is on the driver's side of the engine block to make sure the EVAP hoses are connected properly to it.

Good Luck!