Potterton Profile 80E?

My boiler is approx. 8 years old. When the hall thermostat calls for heat you can hear the boiler try to start up but it then stops again. It will try to fire up again and again and sometimes it takes 5 or 6 attempts before it actually fires up. Once lit, it works fine until the nest time the thermostat calls for heat and then it repeats attempts to fire up. Does anyone have any ideas please?