Nikon Learning Curve

Was out birding today with my Nikon D810 and Sigma 100-600mm G2. Have no idea what I hit or if I hit anything, but when I got home and took a look at what I shot, it looked like I some how did something that was causing a "bracketing" effect when shooting in Quiet Continuous. I had a ten shot max set and most of my bursts where only about 5-6 shots. The first shot looked fine, but then each progressive shot got lighter and lighter like either the white balance or exposure bias was increasing with each shot. After looking at the review data, it appeared that something caused the EB to increase with each shot and it was getting as high as +5 with a full ten shot burst.

I ended up doing a reset on all my settings and then going through and setting up everything again. All good now, but still have no idea what I did to cause the problem. I had used the camera previously with no issues, but after thinking about it, I had only shot in single mode or only took two to three frames in continuous low. Since I bought the body used from Roberts, I'm wondering if there wasn't a lingering setting somewhere that just came to light when taking longer bursts.

Any thoughts would be appreciated in case it happens again.