no water from hot taps

I have no water coming from hot side. cold side ok. had problem the other night. ran cold water for a while, heard "bump", then hot water flowed. i've heard the bump before, in the morning when turning on the shower. flow (hot) would be strong for one second then back off, bump, then normal. what's wrong with my system? Any help is appreciated.

What type/make/model hot water heater do you have?

Does the hot water stop at all valves, or only some? If you go to the WH and open the T&P valve, do you get water out? Many WH have heat traps on them, if they are installed on the wrong port or backwards, flow can force them closed. There could be crud in the line and when flow occurs, it moves to a point where it stops the flow.