2017 Yaris L Strange noise when idling at a stop

[RutherfordmanX]

So this is my second Yaris and I am up to the 70,000 mile mark. For quite some time I have noticed a noise when I stop at a light or the like. It sounds like maybe some kind of Emission purge hum, starts off louder and reduces noise and stops in about a minute or less. Not real loud but noticeable and I don't think I heard it when it was new. Maybe does it more in winter and usually after clocking some miles and stopping, not at every stop. Anything to worry about before it runs totally out of warranty? Other than that I am hoping to go another 375,000 miles on this one like my 2007 (It got hit and was still going strong)