Check Engine Light On problems of the 2005 Buick Lacrosse

A couple months ago it stalled, while my 17 year old daughter was driving it.  there were no engine lights on.  this happened to me a couple times and to my husband.  it takes about 2-3 minutes before you can start it.  the engine light will come on when it stalls, but goes off when started.   without the engine light on, there is no the code to find out what is wrong.  one time it stalled and when started, the engine light stayed on. .  my husband took it to the gm dealer and we were told it was the battery.  we bought brand new battery and installed it.  same day the car would stall.  I have read many stories about this problem with the 2005 Buick Lacrosse.  people seem to have multiple problems it could be, but when replacing parts doesn't fix the stalling problem.  I called gm and got a case number.  we are told to keep driving it until the engine light stays on so we can get a diagnosis.  when the car stalls at 20 mph or 55 mph, you have no control of the vehicle.  gm won't do anything until there is a diagnosis.  I asked gm if I could get a loaner car until my car is fixed and they just say the warranty is over, or it is a seven year old car, and of course won't do anything until it is diagnosed. ??  it is very dangerous, especially if no warning lights come on.  I don't dare to drive it.  my husband is the only one who drives it.  we have another vehicle, which is gas hog that I have to drive.   I can't afford a new car.  I also can't afford to keep buying parts that don't fix the problem.  my car is paid off.  I am disabled and can't work.  just waiting now for disability benefits.  my car has low mileage and is in perfect condition.  I am unable to drive my car that is registered and insured and gm will not help me.  I think it is dangerous to tell us to drive the car until a engine light comes on.  any resolutions?.