This video isn’t mine, but it demonstrates the same noise my 2017 Golf Alltrack has been making for a while now. Other users on Reddit are commenting to say that they hear the same noise from their Golf. So far, no one there has come up with a reason or a remedy, so I’m cross posting here for a little more visibility.
To describe it in words, it is a brief rattling sound that inconsistently occurs at low speed and low engine RPMs.
But late, but I put money on a loose heat shield, probably around the catalyst.
Anyone with a Subaru will know it well (because they need even more holding under the flat 4s).