2013 CLS550 - About 3 weeks ago, when I unlock the car to drive it somewhere, and when I turn the car off and get out of it, there is a 30-45 second air whooooooosh coming from just behind the driver side exhaust. I had my local shop take a look when it was in getting some check engine stuff dealt with (unrelated), and they told me that not only did they not hear it, but that it's likely normal suspension noises. I've owned my CLS for going on 8 years now - I am quite familiar with all of the various noises it makes, including the suspension leveling POOOOSH noises. This does not seem to be in that category - does anyone have any ideas? I am a little shocked that they weren't able to hear this noise, I can hear it sometimes across a parking lot haha. I have noticed nothing abnormal when it comes to driveability, performance, etc. just my guy wheezing his *** off in his advanced age.

Here's a link to the video, I don't know how to embed it into the post (it told me invalid URL) - obviously turn the sound up.

https://imgur.com/a/F70E9f5