This issue happened a while back but was finally fixed in Dec 2017 under extended warranty. Anyhow, everything was good for about 6 months and then bam the rattling noise came back. It only lasts for 2-3 seconds on startup and is fine. Sometimes it doesn't rattle depending on the weather maybe? Anyhow I did have an MB mechanic take a look finally and of course it's going to cost $5-6k to replace the timing belt, and other various parts. What can we as consumers do? For now it looks like I won't be buying MB anymore.