Hi,
Update: 12-2018:
Well, I thought that this had solved my problem BUT IT DID NOT. -Zeek5
Old review:
I had the same issue and stumbled upon the solution by mistake.
I tried hard reset, and it did help for a while, but then the issue started again.
Bottom line - the issue was with the news reader app - News Republic.
The default version worked fine, but an update caused the issue.
I know this because i uninstalled the update, and restarted the phone and everything was OK.
A couple of days later, my phone was left unattended with the WiFi on, and the update re-installed itself. A reset showed the problem returned.
Now the app is forcefully disabled. I can also testify that battery life improved drastically since. I have noticed the battery life got worse after updating to Marshmallow.
Hope this helps someone who is looking for a solution to this extremely annoying problem...