I'm unsure if this is a mac issue or a browser issue, I suspect the former so I'll try here first.
In short, I have a few browser applications that generate desktop notifications. If I lock my mac and within a short span of time, ~45 seconds or less, over 4 notifications appear, the computer won't wake. Once when I walked away, it had even rebooted itself by the time I got back, but I have not been able to replicate this. I don't know if non-browser generated notifications cause the same problem.
This is not a problem while the mac is unlocked.
I'm using a Macbook Pro 15" 2015 running Sierra (10.12.6). My browser is Chrome 65.
I'd appreciate if someone could enlighten me as to what is breaking and how I can fix it, or inform me if this is the browser and definitely not a mac issue.