Australian Car Repair Issues? Ask an Auto Mechanic for Answers ASAP
I have seen this many times on Astra.
Worse case is you will need a new throttle body, easiest case is a vacuum leak at a perished purge hose.
Does it ever have the engine light on after restarting the car?
I would take your car to a Holden dealer or at least a technician with Tech 2 to see what is wrong.
If the vehicle drives normally except the stall condition, my bet is the throttle body.
There is a techline bulletin pertaining to this condition.
Hope this helps.