what is wrong with my baxi 105e boiler?

I have a Baxi 105e combi boiler which was installed just over 3 years ago. During the summer period the switch on the timer for the radiators was in the off position. However, I have noticed that the pump kicks in from time to time for no apparent reason and the rads get luke warm. It does switch off after a short time on its own. I have even turned the switch over to hot water only and the problem still occurs. The only way to stop this occurring during the night is to swich the boiler completely off. Nothing has flashed on the fault finding panel so has anyone any idea what the problem could be?

Peter Rochester
September 2007