there is honestly so many things it could be, ideally you need to get it on a renault diagnostics machine.
it could be anything to do with the fuel system / injection process, so fuel pump, injectors, fuel filter, plugs, boost leak etc etc
Current: Dynamique DCi 80
Owned: DCi 65, 80, 100 and GT DCi 106
Current Toy: Clio 182 Trophy