Xposed Framework is getting more and more stable for both Lollipop and Marshmallow. Xposed is the app for root users that allows you to fully customize every aspect of your Android device. There was apparently a huge issue with Xposed Framework that was causing random reboots. This has been fixed in the latest update. Many other fixes are also include mostly concerning all kinds of issues causing reboots and freezing. Head to the link below for the download links.
via Xposed