I recently bought a house which was winterized. to dewinterize it I opened all the upstairs faucets. Turned on the water and opened the downstairs faucets. The waterline to the hot water heater was opened too. Then I opened the hot water faucets and let those run. There was sputtering at first then It ran normally on both sides. The only valves i had to open where the main water line and the hot water valve in one of the upstairs bathrooms.After this I turned the electricity on to the hot water heater and in a little white I had hot water and sputtering in all faucets. It went away if i let them run for a while. Now everyday when I wake up the hot water runs cold and its fine then there is sputtering, really loud and spewy sputtering when i turn on the hot water in any sink. After a while the water stops sputtering and gets pretty hot. I have to repeat this process in any sink/ faucet I use. The cold water is fine and doesn't sputter. Its the same when I get back from work at night. Any ideas what might be causing this or how to fix it?