car cuts out?

Hi anyone help i have a vauxhall vectra 54 plate 2.2 dti.car cuts out once a week no engine magement light on, when it cuts out it starts straight up and idiels but sometimes it won't rev then starts to rev eraticaly then cuts out again, after the third time starting it runs like a dream for a week then cuts out again,but always starts first time and idiels. vauxhall say they cannot do anything until the light comes on. cleaned the egr valve no improvement. its anoying