Engine stalls

Hi, I own a new Toyota Vios J spec and I started to encounter a problem recently. To be more details, Started the car and travel for either long or short distance and no problem, then when I switch off the engine and restart after maybe a few second, immediately the engine die off. Started again, engine die off. Have to start approximately 3 to four times then only it works.(These die off thing only comes once a while, not everytime) Have send to a Toyota service centre to check and they use a computerise gadget to check and the results says dtc problem, ask to recheck the wire and they fix it back, But I still encounter these problems. Can anyone please tell me what is the problem as I understand its hard for those toyota technician to check cos the car doesn't always act like this. The mileage used is only 18000 km. Thanks in advance