how can I fix the problem?

Hi there, I have a 1997 2.00ltr petrol seat Alhambra and the engine stops after about 7 miles if it is left to cool down for 10 minutes it will start and then it will travel for about 1.5 miles before it will stop again , any one got any ideas on this as it would be very helpful. I changed the relay No 30 and it ran fine for about 2 weeks before the problem came back thank you