Humming noise on a morning

[trannyvanman16]

Hi guys need som advice got a transit mk7 2.2 2012 and when I start it from cold it runs fine then developes a humming noise heared from the driver's side area when stood still I'll add. If I rev it a fraction it goes then let of and it comes back. If I drive around were I live it goes and doesn't come back then all day untill it's cold. But it doesn't sounds nice on a morning.
Any ideas please
Transit mk7 fwd 2.2 2012