When I turn on the hot water the water starts and stops coming out and the pipe bangs. I can get it to stop banging if I turn on another sink or turn the hot water up all the way. This doesn't happen with cold water. Once the hot water is flowing the banging stops.

Does this only happen in one fixture, or every fixture.

It happens in every fixture

Do you have a hot water tank or a combination heating and domestic hot water boiler?

And do you heat your water with gas or electricity? Back to you, Tom

It's a gas hot water tank, high efficiency

My guess would be that you have a loose washer in the cold water input stop valve to the water heater. Try closing the valve about half way and see if it makes any difference.