What is wrong with my boiler?

Hi,
I have a Ferroli Optima boiler (not sure of the exact model) controlling my heating and hot water. For the last few months it has been making an awful lot of noise when running. It sounds as though the unit is vibrating violently. Additionally, in the last few days, when using hot water the boiler will fire up (making the same noise) and produce hot water for two minutes, and then will shut down and fire up again in approximately 10 second cycles. Apologies if this is incomplete in detail, I have ABSOLUTELY no idea what I am doing. I would call out a plumber or the like, but to be perfectly honest I don't have the money. Any ideas what would be causing this, and how I can fix it? Or at least how much would it cost me to get repaired professionally? Many thanks in advance.

Mark