my vauxhall zafira 2.0dti 02 modelstarts ok drivesok but when it warms up a?

my car starts just fine , and after 20 - 30 minutes the engine cuts out and it makes a 1 small low noise, and then it turns on again if you try to turn it on. but the computer sais"stop watch OM1N 0,0s we dont have a manual to try and find what it means. does anyone have a manual to tell me what this posibly means or what is wrong with the car