Hi, I have a boiler that also supplies the hot water to the kitchen and bathroom. Over the past 2 weeks, I've noticed a rattling noise coming from the pipes. It happens only in the mornings when turning on the hot water in the kitchen. The water spurts out and the noise gets louder the more I open the faucet.

I also noticed that the radiator in the bathroom wasn't getting hot so I bled out all the radiators. It helped but the next day I had the same issue. Right now, I am bleeding the radiators once a day but there has to be a better solution. What do you think it could be?
Thanks.