Honestly, unless you are in a stripped down environment like safe mode, there really IS no such thing as "idle". There is always something going on, and even if it seems like nothing is going on for a few seconds, unless you have taken careful steps to completely minimize ALL background processes and startup programs to only those that are essential, there will always be some kind of processes starting, stopping, waiting for triggers, performing tasks, etc.
Core and package temps at "idle", meaning YOU are not intentionally running anything, no browser windows, all non-essential processes like game loaders in the tray, disk optimization (Automatic defragement/TRIM), system restore, either exited, ended or service killed, will STILL result in many background processes running. Just open task manager and browse through the Processes tab to get an idea. So, even then, if you have very minimal processes running and NEAR zero CPU resources being used, you will still usually see significant fluctuations in various core speeds/usage, temperatures going up and down, voltage changing based on core clock changes, etc.
Your numbers STILL seem normal to me. Things like Windows checking for updates, system restore making restore points, disk optimization running defragmenter or TRIM, OTHER programs, games and applications doing their thing checking for updates, browsers checking for updates, plus all the hidden Windows processes that are doing their thing behind the scenes, means you will never see a CPU just sitting there on a zero fluctuation 800mhz clock for very long, and when the clock goes up the voltage goes up to keep things stable. And when the voltage goes up and the clock goes up, the temperature goes up in kind. All very much normal.
Now, if you start seeing HIGH CPU USAGE for no reason, or processes in Task manager that you can't account for or find any information about, then it's time to start looking for infections or rogue programs. As it stands, there's a few things I'd do.
One, make sure your motherboard BIOS is completely up to date, unless you have a very good reason for NOT installing a specific BIOS version. That is rare, but it happens from time to time.
Two, make sure you have MANUALLY installed all of the relevant drivers for your motherboard from the motherboard product page on the manufacturers website.
All of these should be installed unless there is a good, specific reason for not doing so such as known conflict problems between a hardware specific driver and some other hardware on your system.
Install in THIS order:
Z370 Aorus Gaming 7 chipset drivers:
https://download.gigabyte.com/FileList/Driver/mb_driver_chipset_300ser_infupdate_10.1.17969.8134.zip
Realtek driver:
https://download.gigabyte.com/FileList/Driver/mb_driver_audio_realtek_8586.zip
Install BOTH of these LAN drivers, however, I recommend that you USE the Intel network adapter as I believe it is the better of the two. So figure out which is which and plug your ethernet cable into the Intel ethernet socket.
Killer LAN driver:
https://download.gigabyte.com/FileList/Driver/mb_driver_lan_killer_2.0.1125.zip
Intel LAN driver:
https://download.gigabyte.com/FileList/Driver/mb_driver_lan_intel_23.5.zip
ASMedia USB 3.1 driver:
https://download.gigabyte.com/FileList/Driver/mb_driver_usb31_asm_300series.zip
And I recommend that you update to the F14 BIOS version.