[SObmw]

I have an '07 e90 with the straight six non turbo engine

I notice that when I start the car, every time hot or cold, it makes a rattle noise for just a split second when it starts.

When you push the start button the tach jumps to like 900rpm and instantly drops to 600ish rpm for idle, just like any car when it starts. Only it makes a rattle when it does and only for that second.

If I rev up the engine it's like butter. No weird noises smooth as can be.

So is this normal? Is this a sign something is going out soon?? The car has only 46,000 miles on it right now.

Thanks for any input!