Started getting a buzzing noise that sounds like it's coming from the driver side footwell area up under the dash when starting the car. Continues when i rev engine and goes away when warmed up? I have searched the forums but haven't found anything yet.

I had this a few times with my 3.6 TDV8 across the course of more than a decade. Starts like a buzzer and eventually fades away to nothing across about thirty seconds. It only happened a handful of times and it always left me perplexed. Nothing about the car seemed to be affected by it, but it was disconcerting at the time.  The older I get, the more I realise that people confuse wrinkles for wisdom

Fuel fired burner heater? 2018 SE SDV8 4.4 Byron Blue

Was there not talk about the heat shields around the gearbox / exhaust areas rattling sometimes ? Maybe something like in particular temperatures that its rattling / buzzing, but with a slight change of heat goes away ? V8 or else ...