My boiler comes on when not needed?

My boiler( Glow worm 38cxi) comes on at 4.30 some nights although it is not frosty, a friend has checked that the programmer(Climapro) is set right ?? Apart from the expence and wakeing up to the heat I am getting up to find that it has turned itself off again. This is causing me to then worry what is happening and unable to go back to sleep HELP PLEASE