There is no such thing as an auto choke on your car.
I would suggest your problem is the Engine Coolant Temperature Sensor There is a sequence I could give you to test the sensor but it would be easier just to change it. This is the most likely cause of your problem however there are a number of things as well that it could be.
Ign system/Ign timing
Fuel Pressure
Throttle Posistion Sensor
MAP sensor
Engine Control Module.
Having said all the above is there an Engine management light on if there is you can easily extract the code which will pinpoint to the problem.
chris
December 2005