I noticed when driving slowly through a parking garage that my car (2016 GS-350 F-Sport) would make a hissing sound while driving forwards. I didnt notice the sound when turning, only when moving forwards. Its not a constant hissing but instead intermittent. Note: I was not pressing the brakes when I heard the sound

I wish I had a good service place to go to. Not really fond of my local dealer but might have to suck it up.

 

@jms123 difficult to diagnose without hearing the sound. My first inclination is you have a serpentine belt that needs to be changed - but if its the belt, the sound should be there when you are in park/idling (not just in drive).

Alternatively, there may just be something lodged between your brake and rotor grinding against the metal as you move...this happened to a family member and after a thorough powerwash, whatever was there was dislodged and the noise went away. You can put in drive, turn your wheels full lock left/right and hit the brakes swiftly a few times...try doing this in reverse as well.

Otherwise, unfortunately, the best thing to do is have a local shop or your local dealer inspect it.