Starts then it's has convulsions n shuts off
My car has 70000 miles.
My car has an automatic transmission.
This may be caused for many different reasons, such as a misfire or a lack of fuel (which can also cause a misfire). The lack of fuel may be caused by low fuel pressure, dirty fuel injectors, bad connections to fuel injectors, a faulty mass air flow sensor, or many other things.
I would recommend having an expert mechanic, such as one from YourMechanic, come to your home to diagnose why your car is shutting off in this way.