Z170 Extreme7+ Shut Down Problem

One missing bit of important information... the OS and version you are using.

I'm guessing it is Windows 10?

I have the same mother board as you do, and I use G.SKILL memory running at 3200, and I can OC it to 3600. But I don't have the issue that you are experiencing.

Your symptoms are different than we usually see, with a system running on normally immediately after a shutdown. This has become an issue that I won't call common, but has been seen enough to be known to us. I'll mention a few things that could be the cause. Please read all of them before deciding what to do.

One cause of this is the Windows Fast Startup feature, introduced in Win 8.

If you'd like to try this, it can be disabled by first opening the Windows Power Options, normally used to choose or modify a Power Plan. On the upper left of this screen find and select the "Choose what the power buttons do" option.

You'll likely need to click on the Change settings that are currently unavailable before you can disable the Fast Startup option. Then uncheck this option under Shutdown settings. You'll need to shutdown normally (if possible) before this feature is disabled. You can enable it again by simply reversing the process.

The only time I had a similar issue is when I used a program to clone an OS installation from one drive to another. That was using Macrium Reflect, although I really do not know if it was the cause. The only fix I found was a new OS installation.

A simple potential fix is clearing the UEFI/BIOS. You could do a full clear by moving the jumper to the clear position, and removing the board's battery. Just removing the battery will not provide the same results as doing both. Don't forget to save your UEFI/BIOS settings in a profile before doing this, if it is difficult to reset them from your memory. One potential issue with a saved profile is...

A setting in the UEFI might be the cause. The Deep Sleep option in Chipset Configuration is best left at its default setting. Did you happen to change the Restore on AC/Power Loss option? Just curious as a potential cause of this issue in general.

Do you have the Intel network driver installed? Win 10 (if you use it) does not get along with the Intel networking driver in some ways, and still does after several releases. Disabling the various Wake on LAN options in Device Manager might help.

I suggest checking the wiring of the power button on the PC case to the system header on the board. While the polarity of this switch may seem irrelevant, I leave nothing to chance. Do you think the wiring and switch in the PC case is in good condition?