2 litre petrol or diesel you have?
Any warning lights or messages in info screen pop up since this occurred?
have you had any recent work carried out on the car?
If your refering to sticking valve causing compression loss resulting in missfire..is one possibility but it would be hard to actually diagnose that without getting a proper compression test done on all 4 cylinders to see if thats the case or not then leading to leak down test to see which valve is at fault..not easy on the HDI's as you would need to test via the glowplug orifaces and removing them would need some care to avoid snapping..removing injectors can be tricky especially if they are siezed solid in the head.normally you need to hydraulically pull them out and even that cant be guaranteed if the cylinder head gets damaged....going by what your saying id be leaning to a possible injector fault a mechanical spray problem..check to ensure the oil level hasnt increased due to overfuelling .. to check injectors you would need to get those tested,leak back and such before any work is done..id say that would be your first step from here..most well equiped garages should be able to perform that test and see what that brings up..
Normally that would come up as an "Anti pollution fault" having said that If the DPF was restricted you have a severe lack in power leading to cutting out..but you would have warnings up to verfiy that aswell as fault codes...added to that your car would likely have an Eolys additive fluid thats already injected into the fuel to help reduce DPF issues...If the car is missfiring severely both hot and cold as your describing to me..giving it run like that wouldnt be advisable in my opinion