annoying humming vibration coming from boiler flue

afternoon all

can anyone help please

i had a new central heating system put in my house when i bought it last year,and for the last 6 months there is an annoying humming vibrating noise coming from the flue it only use to be when we put the hot water on and now it has started when we put the heating on and it will not stop if i go out side and put my hand on and off the outlet it stops but then after a few mins it starts to come back again if i turn the heating off it stop also

what can this be please advise

Paul

And the boiler make & model is ?????????/

sorry

baxi duo-tec combi 40 HE A

Please is there anyone who can help, so i can tell the boiler people what it might be

the humming is becoming very annoying now