Sounds like the ECU is losing its referance data, common cause is a faulty crank position sensor, this provides data to the managment unit so it knows the cylinder position to allow fuel injection and combustion at the correct time, without it serious damage could occure hence the engine shuts down, however this should flag up a code, about twenty quid to fix it yourself or fifty at a garage, may not be the fault but gives you something to investigate online.