System Hangs on Shutdown + System Interrupt CPU Use + Startup Problems

I'm having a set of problems that I can't find an answer for.
1. After choosing the "shutdown" command, the computer stays on the blue "the system is shutting down" screen forever--two days or more--until I hold down the power button for several seconds.
2. On startup, most of the system tray icons (dropbox, network connection, antivirus etc.) don't appear.
3. Task Manager shows a "system interrupt" process using about 99% of the CPU.

The problem can be solved temporarily by doing this:
Powershell as Admin --> "sfc /scannow"

After that, the system is fine at the next startup, but after 1 or 2 startups more the problems reappear until I run SFC again.
From reading other people's reports online it seems people sometimes solve this kind of thing through the Device Manager, but I don't know how to tell which--if any--device or driver is causing the problem.

I have a system restore USB, but am hoping not to do that because I don't want to go through reinstalling all my applications.

The machine is a Samsung NF210 netbook running Win 10, with all the latest updates. Samsung's website doesn't offer any drivers more recent than what's on my computer.

Any ideas?

mostly this kind of problems are being caused by virus/adware/malware etc.
It can also be an "update" or "update checker" process of an application.

You could check ,by monitoring processes, wich process is using the most CPU and/or RAM.

Run device manager and look for yellow warning icon overlays. try to disable the device, and see if the Task Manager performance indicators show a drop in CPU usage from System interrupts.
Re-enable the device and run msinfo32, and look for hardware resources, conflicts and sharing - see if the problem device is sharing as a triplet, or twin with another device - if so disable that other device(s) and consult the resources. you may need to disable more than one device. Test shutdown.
Once you have a working system without interrupts preventing shutdown, or warnings in DM, you will need to find solutions to renable them without conflicting with other hardware - usually in the device properties.