I have a combi boiler providing hot water in my house. If I run the hot water (e.g. in my shower or kitchen sink) it comes through hot just fine after a couple of seconds and stays hot however long the water is running. However if I turn the water off for a moment - say 10 seconds - and then turn it back on again it will no longer come through hot (or it's hot for a few seconds and then...) but comes through cold and may not warm up at all. I can get it to run hot again by turning the water off again and then waiting a few more seconds and turning it back on and it will usually warm up again at that point though sometimes it takes multiple tries.
Any idea what's going on with that? It seems strange