If you’ve been having problems with your Galaxy Note 4 lately – lagging, freezing and randomly rebooting, this could be probably be due to a bad update by Samsung.
Error on boot up like: “could not do normal boot, mmc_read failed” showing the black screen Android character could be frustrating and the constant reboot just forced me to get an S8+ instead.
So for a temporary fix, that will completely allow you to normally use your phone again, try downloading Wake Lock Power Manager from the Google Play Store. Run the PARTIAL_WAKE_LOCK mode.
I have done this and the phone again is responsive, and doesn’t restart randomly anymore. Try to read the Reviews of the app and see for your self. Let us just hope Samsung releases a permanent fix for our Note 4. Goodluck!