Ariston combi boiler problem

Hi I have an Ariston combi boiler that has a couple of problems.The boiler is a about 6 years old. Recently the hot water tap after an initial run of 15 20 seconds goes cold for about 60 seconds before getting hot again. The other problem is the boiler seems to fire up about once an hour for 5 - 10 seconds for no reason. (I know it is supposed to do this when the heating is switched on. but this is with the heating off) anyone got any ideas to what the problem might be? Cheers

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