E30 Zone

Hi I have a 325i my sport 2003 m54 engine
Would anyone know why my temp gauge gose up to fast it sits in the middle as it should but from start up in the morning to a mile down the road it right at working temperature or so the gauge says also after a drive I park the car up and I can come back hours later and boom temp gauge right back to middle???

Anyone any ideas????

Ignore the gauge, E39 temp gauge is pretty much useless. Between 60 odd °C and 116°C the gauge sits in the middle, for an accurate reading use the buttons on the clock to give a digital readout, hold the button on the right until the menu comes up, then press it until test 7 shows then press left button.
It may be a faulty temp sender but compare the digital readouts first

Someone previous to me owning the car has put a aftermarket stereo in

The clocks/instruments in front of you I meant

Cool cheers mate