Wired noise when engine is cold

Hi and Happy New Year

I have a 1.2 petrol automatic micra 56 plate

The engine is in a very good condition as only 13k on the clock

Since I bought the car when you start the engine and its cold I have blue light on the dash indicating that (nothing wired about that). It only take a couple of minutes of driving for the engine to go into normal.

When the engine is cold the rev counted shows minimum 1500 rmp when the car is stationary. As soon as the light is gone and the engine is warm it goes down to 800 rmp.

When driving whilst the engine is cold it make a noise like I am revving it a lot although usually I don't go past 2 500 rmp.. again as soon as the light on the dash is off the engine is super quiet. Also I haven't noticed any power loss when the engine is loud.. nothing strange apart from the noise!

Is someone else's micra doing the same?

Thanks for your input guys!
yes I've got the same symptoms exactly on a 14k miles engine. Engine has only been used once a week for last 15 years by my mother.Since
I've inherited the car and run it for more extended sessions it has developed this cold rattle. Engine is very sweet when warmed up after a minute of running. Dave