Engine cut out whilst driving on Master Dci 2005 reg

Hi,



I have a Renault Master DCI LWB 2005 reg and I have this annoying problem - engine cut out whilst driving. It could happen anytime, at any gear and probably 5-6 times a day.



The whole van loses electricity. Everything stops. I turn the key back and can start the van every time but it's dangerous.



Any ideas?



Thank you.



Nick