Random PC Restarts, Game Crashes, and Failed Windows Updates—Could RAM Be the Problem?

I've been dealing with persistent problems on my Windows 11 PC and have run out of ideas. The system randomly restarts, sometimes while I'm only browsing files. Games crash regardless of how demanding they are, with missing textures or simulations stopping unexpectedly. Chrome tabs also crash, and Windows updates frequently fail or refuse to download automatically.

The system has an Intel Core i7-9700K, ASUS PRIME Z390-P motherboard, 32 GB of DDR4 memory, a Radeon RX 9070 XT, and several SSDs plus a 4 TB hard drive. I've already replaced or upgraded the SSD, graphics card, power supply, and RAM, although the problems started before those changes.

So far I've updated the drivers, performed a clean Windows installation on the newer SSD, formatted the previous system drive, and run CHKDSK. Could another component—especially the memory, motherboard, or memory controller—be failing? What should I test next?