You do not say the make or model of the boiler and do not say how long a "while" is...
I am not experienced or qualified to give sensible help - I would guess the overheat thermostat is intermittently tripping out and by resetting it the boiler can carry on working.
I would try to overcome this by lowering the boiler thermostat half a notch and or tweaking the speed of the circulating pump to make it run faster - but I know nothing - all guesswork.
Good luck...
Peccavi, December 2010
