Usually, updates improve an experience, but that isn't always the case. For some, the recent upgrade to Android 8.0 Oreo seems to have come at the cost of stability. A large number of people have reported frequent random reboots occurring since they made the jump, including some of us here at AP. 

Our own Artem was experiencing the problem almost daily, so we did a quick poll on Twitter to see how many of our readers were affected, and the post garnered a significant number of positive responses. Although many people aren't having any problems on 8.0 at all, no small number are experiencing this particular issue. There was some hope that the September OTA might have fixed things, but that doesn't seem to be the case.

The problem was reported to Google's Issue Tracker during the developer previews, but was marked as "Won't Fix (Not Reproducible)." Our informal polling seemed to show that most of those affected are using Pixel XLs, but both the number of reports and the device diversity of the audience may not be large enough for any concrete connections to be drawn.

Some have reported that returning to Nougat fixes the problem for them, so that's one potential recourse. In the meantime, those of us running 8.0 Oreo should probably keep an eye out for unexpected reboots.

Source: Twitter (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), Google+, Google Issue Tracker