Your desktop icons change because, for a reason unknown to me, when your computer restarts, your screen resolution starts off with a default resolution that is much lower than the resolution you have chosen in your graphics driver. Immediately after that, your chosen screen resolution takes effect.
For that instant that your monitor was displaying at a lower resolution, the icons became much larger, so there was simply no space on your screen to fit them all into the arrangement you previously had. Instead, the icons had to get out of each other's way, so they went anywhere they could find space. As a result, you look at your monitor and say "what the ...".
This typically happened in older versions of Windows and/or with older graphics drivers, when a driver was being updated. I haven't heard of it happening for a while, but it sure looks like it happened to you.
Your screen's resolution is setup early in the boot process. If you have ever made any adjustments in your graphics driver or other graphics software, that might be what's causing this. It could be something totally innocuous, but with a strange side-effect.
One way to check is to uninstall and reinstall all your graphics software (driver and any accessory apps) following the developer's instructions very carefully. But before you do that, here's something to consider: I presume that you are using your computer's graphics card to create graphics. Your computer almost certainly came from the factory with a graphics chip (often from Intel) built into the motherboard. You need to disable this onboard graphics (as it's known) in the BIOS. Otherwise, the computer will try to use both when it restarts.
Hoping for success!