I also had this issue. Every morning after switching it on I could feel the phone quite hot in my pocket. Hot enough to make it really annoying. Did a clean install and although it was a pain in the back side reinstalling apps and restoring photos, contacts etc, it worked a treat. No more heating issues. Also the battery seems to be lasting longer. After 6 hours switched on,I was on 75% tops. After reinstalling marshmallow I'm normally around 90-95% . Best advice I ever read around here.thanks