The boiler lights ok and begins to heat the water...
After 5 - 10 minutes burner and pilot extinguish...
1) Has the water reached the required temperature?
1a) Is there a "stat" on the hot water tank and what is it set to?
2) What do you have to do to get it to run again?
3) Does the pilot usually stay on when the hot water is "satisfied"
A skilled and experienced person might have an answer for you but being unskilled, inexperienced and consequentially, potentially dangerous - I'm not clear about the actual problem.
My boiler keeps going out (burner & pilot) after it's heated the water - then the water cools and the boiler automatically lights up again. It stays on for 5-10 mins while it's heating the water and stays off for a longer period. It does this until the timer programmer says stop.
Peccavi
May 2009