car won't start up when switch off when normal temp ?

got a ford galaxy 2008 2L tdi
when you start up when cold it starts,
but when you get it to normal temp switch off then wait a couple of min like goto shop then go back too it, it does not start up, you can wait 10min before it starts up, its like the engine cool down, or something not opening up before it does.
dealer don't know they say it's fix but not
i don't think they know