Generally the Microsoft installed HD Audio Codec does not have all the features the motherboard vendor's sound drivers do. In most cases the actual driver is preferred and should be installed instead of the generic HD Audio Code drivers.
The NVIDIA driver is for the Video and the build in audio for HDMI audio. It should not be interferring with the PC's sound and in this case Realtek. I would uninstall the Microsoft drivers and reinstall the RealTek and see if you still have the problem. Generally a driver causes problems when exiting from sleep mode. Actually on "extended" sleep mode of overnight its really better to just shut down the system and then reboot in the morning. If you want it to be operational when you wake up, the BIOS should have an option for auto power on at whatever time you set.