Whirlpool Gold Microwave vibrates while not in use

I have a Whirlpool Gold Microwave that started vibrating/humming while I was boiling water on the stove. I turned the fan on and the sound stopped. When I turn the fan off the sound comes back. It’s a very loud sound and I can feel the microwave vibrating. This has happened a few times in the past but running the fan for a few minutes would take care of it. It always seems to happen with high humidity or boiling on the stove. The microwave still works even with the sound/vibration. Any ideas?

I also have a Whirlpool over the range microwave that has the exact same problem. When I boil water on the back burners on the range the microwave starts buzzing. When I take off the top vent and filter I can see the exhaust fans slowly turning. Any help or suggestions would be appreciated.