Why does my BMW 4 Series make a rattling noise when I start the engine?

Every time I start my BMW 4 Series, it makes a loud rattling noise for a few seconds before it goes away. It only happens on startup, but it's been getting louder. What could be causing this and is it something I should be worried about?

It's possible that the rattling noise is coming from your engine's timing chain. This is a common issue in 4-cylinder BMW engines, and if not addressed, it can lead to more serious problems down the line. I would recommend taking your car to a mechanic as soon as possible to have it checked.

Another potential cause of the rattling noise could be a loose heat shield. This is a metal panel that's meant to protect your car's exhaust system from excessive heat. Over time, these shields can become loose and start to rattle. A mechanic can easily fix this issue for you.