If its the crank shaft sensor the car would be missing on initial revs (from 0-2000 rpms) Not entirely shut down and not start again. ( i had missing issues in my baleno for over a year, Found out the CNG guy has cutted the current wire to CrankShaft sensor.
The turning off could be related to TPS (timing position sensor) that get faulty in CNG vehicles because the timing is very much messed in them. But that would cause the car to go off in the middle of no where (just when the sensor is heated) and car wouldnt start unless the sensor cools down.
Mind you all these sensors dont cost too much, If you or anyone sugests you to buy them from scrap, Atleast for once take rates of new ones then opt for scrap ones.