What is the greenish yellow LED?

[AC Question]

Hey there, so I got a Nexus 5X about a week ago, and a day or two ago a flashing greenish yellow notification LED showed up. There is absolutely nothing in my notification bar, and I've checked any apps that night have that color of LED. Nothing changed before it showed up, I just restarted my phone and there it was. It's getting annoying, plus it keeps waking my screen every two minutes, which is both annoying and a drain on my battery. Any ideas what it is and how I can get it to stop? Thanks!