53 plate peugeot 1400 hdi,?

have a 53 plate peugeot 1400 hdi, when you go to start it you turn the key and it fires and revs first time but after a few seconds (3-5) just cuts out you then have to turn it over for ages untill the batt is nearly flat before it fires again, then it runs perfectly and drives perfectly untill you leave it more that 3-4 hours then same again......changed fuel filter wonder about fuel cut off switch....help please.....