Inspiron 5402, pulsing fans (also small fingerprint issues)

Recently purchased this laptop and overall, pretty satisfied. I did however notice that regardless of the power setting in the Dell Power Manager app, the fans will ramp up and down constantly. It would be pretty loud for about 5-10 sec, noticeable for another 30-40 sec, and then turn off for about 1 min and loop like that. Interestingly, I noticed that switching power modes while the fans were running would stop the fans.

For reference, according to the Dell Software Update, all my drivers are up to date, BIOS is up to date, all windows updates went through. I've changed the System Cooling Policy to passive, turned off turbo boost, and I notice this behavior with low CPU usage 5-10%. 

Has anyone experienced this issue on their units? It's not enough for me to consider returning the laptop, but if anyone has any guidance on how to solve it, I'd really appreciate it!

-- Side note: has anyone noticed that the fingerprint sensors on Inspirons (located on power button) never seem to work first try? Even when I'm setting it up, it tells me that the sensor needs cleaning. Don't really know how this could be the case since I've barely touched the power button in the week I've used the laptop. Any guidance here would be super helpful too!