One of my PC parts is likely on the way out, how do I narrow down which one?

Hello, lately my PC has been crashing in all manner of ways, sometimes it forcibly auto-restarts, others it brings up some error code. In one of the more recent crashes, my pc's Ethernet adapter seems to have stopped functioning correctly. It will identify the Ethernet cable, but for one reason or another will not connect to the internet. The Ethernet itself isn't the problem, as connecting it to a different system with an Ethernet cable has it function perfectly. I have a suspicion that one of my arts is about to give out, and while my eye's on the Motherboard, I'd like to make sure, how can I narrow down which art it is so I can figure out the most cost-effective means of replacing it?

My current specs are:

Motherboard: MSI 8450M PRO-VDH MAX
Processor: AMD Ryzen 5 3600 6-core, 3600 Mhz
Ram: 24GB
GPU: Radeon RX 580

A strange thing I found just by looking for this, is that the RAM seems to list itself as 24GB, but I had 32GB installed.