Sometimes when my wife is doing laundry the gas clothes dryer will
start making a loud noise. This doesn't happen right away, but after
sometime. It doesn't do it every load, but once it starts doing it
doesn't stop unless she stops the machine and waits a while. It seems
to be a vibrating type noise

I checked the the exhaust duct and there isn't any buildup. But it
keeps taking longer and longer to dry.

Thanks in advance for the help.
-Dan