The engine check light suddenly goes on and then the engine switches off.

Good place to start is a scan test .... While the engine will NOT start is when more involved testing must be done! First an ignition spark test is required .. IF that is ok, fuel pressure test is next... I prefer testing as opposed to guessing at which part to replace as testing is usually the least expensive route to take .. Some might say main relay while others may say ignition switch .. Both are certainly possibilities however each one has different test proceedures that must be followed to 'confirm' IF either is the culprit .. Then there are even more possiblilties that will cause the exact same thing .. Got to be tested! .. Good luck!