2012 Cls550 chirping noise passanger side

Started having a chirping sound from passanger side of vehicle. Its intermittent and does not seem to be from hvac. It still happens if ac or air unit off. It seems to do it while am driving, for this reason i cant troubleshoot it. While it is parked i cant hear it. I have alittle under 50k miles and always dealer maintained with no issues. The serpentine belt and idler look ok. No visible tears.

Thanks in advance.