Yes, I bought all of the parts online from a few different places, and they were all new. Because of return policies, I know I can't return my Ryzen, and I'm not sure about my other parts, but I probably won't bother.

Thanks for the info Gabethebabe, ionutd, adios, donfairplay.

I just tried disabling secure boot, but it did not help unfortunately.

I guess one more thing I can think of to try
in bios, manually cap the cpu freq to base 3.7 Ghz
mby the bios is stupidly set up and sends too much voltage at some point and chip says no thanks and cuts off
or do it the other way around, leave freq on auto and set voltage manually to a safe value like 1.35v

I see in the bios that the cpu freq is already 3700 MHz.

I did try to set the voltage manually, but I don't know if I did it right. I went to the BIOS, then Advanced Mode, then Ai Tweaker, then I changed the VDDCR CPU Voltage from Auto to Offset mode, then I made the VDDCR CPU Offset Sign "-", then I tried several different values for VDDCR CPU Offset Voltage. I got the voltage to around 1.35 V or lower (and I saw the CPU temperature at around 40 to 45 instead of 55 degrees Celsius). This did not help though.

In fact, it was probably just a coincidence, but I thought it was making the rebooting worse (i.e., make the rebooting happen earlier), so I made the VDDCR CPU Offset Sign "+" and I tried different values for VDDCR CPU Offset Voltage. I probably should not have done this though because too much voltage is bad? I don't think I got it above 1.52 V though and I didn't see the CPU temperature above 60 degrees Celsius in the BIOS. With the VDDCR CPU Offset Voltage at +0.08125 V, I was able to boot Windows and I was on the desktop for 10 minutes. I didn't really know what to try, but I was able to open Task Manager and look around, and I was able to use the calculator. It automatically rebooted after 10 minutes though as I was typing the password to the WiFi. It was probably just a fluke though because I couldn't do it again, and the computer kept rebooting quickly.

I put the settings back to default, but it seemed like I might have somehow made my system worse because I was not always able to press Del or F2 to enter BIOS and the system seemed to freeze a few times. Before, I was consistently able to press Del to enter BIOS. I cleared the CMOS and now it seems I can enter the BIOS easily again I think.

whatever you do, don't go over 1.45V if you're manually playing with voltage
too little voltage can cause the cpu to not have enough juice and your system will crash but too much can and will fry the chip

I've experienced annoying restart loops before, that lasted a few days, but either caused by bad ram or bad ram compatibility (not same sticks in left and right channel) or more commonly, corrupted drivers due to windows updates

yours really sounds to me like an electrical problem somewhere on mobo's circuitry.
could be the psu as well I guess... seasonic are pretty much the best psus but hey, even with very good quality control, some units can be bad. could also be a bad cable...again, not that seasonic ships their products with cheap cables

I think ram you've eliminated, I've personally never seen a bad cpu that didn't have anything wrong with it physically or just died of old age/over voltage
if you had a 2.5" ssd, you could have replaced the sata or power cables, but no cables on m.2
gpu errors don't act like that

next to try for me would be
1. try other previous bios versions (that support Ryzen 5000 series, if any)
2. pull out the front IO leads from where it says Restart (you know the cables that connect the mobo to the buttons on the front of the case, one of them is for restart, mby that's acting up)

Damn. What would you guess is the likelihood that I damaged my CPU yesterday? Now when I try to boot up, it often freezes on "Preparing Automatic Repair" with the TUF Gaming logo and with patches of blue rectangles on the screen. Before, the reboots mostly just kept repeating (and seemed smooth) and freezing was rare. Now, it's basically the other way around. I can get into the BIOS fine though.

1. I tried to use the Asus USB BIOS FlashBack (which is how I installed the latest BIOS) to install an older version, but it didn't work. Nothing happened after I plugged the USB in and held the FlashBack button. I think Asus doesn't allow you to downgrade the BIOS. I searched online and I couldn't find a good way to do it.
2. I'm not sure if this is even worth trying because it wouldn't explain the times I got BSODs or when the computer freezes. Also, the computer never reset when I was in BIOS. I don't really know though.

I think it's a good time for me to give up now.

take it to an electronics repair shop
it will take a bit of time to diagnose and RMA what's faulty but you will have a working pc eventually, you didn't just spend a ton of money on a dumb metal box
you're quite unlucky to have to go through this but it is what it is
gl, let us know what happens

Just a quick confirmation, but you're not trying to load the corrupted windows 10 install right?

You should be disabling secure boot to try another clean install. With secure boot enabled Windows wouldn't be installing/loading some critical drivers and defaulting to automatic repair to find them on bad installs (your previous corrupted windows 10 install).

Also, I'm not sure why you're messing with the voltage on the CPU... I agree with taking it to a tech, you already spent $x,xxx on parts.

When I tried disabling secure boot, I tried both Windows and then Linux Mint from the bootable USB I made (which I think is not corrupted).

I searched the thread and can't find any reference to it, but you have tested the RAM using Memtest86? Did it manage to run OK or crash?

Also have you checked that there are no case studs (ie: where you attach the motherboard to the case) that are touching a part of the motherboard with no screw hole in it?

I think you're probably at the stage where you should just try and take it to somebody who can test each part for you separately and then you can find which part it is via a process of elimination. Fiddling with things like the CPU voltage out of desperation is only gonna lead to possibly ruining a working part and very unlikely to actually be the cause...

Juk

No, I did not do that test because I don't have access to another PC. I think the problem is probably not the RAM because I tried 2 different types (with single stick tried in more than one slot).

I actually only installed 8 out of 9 motherboard screws because for some reason I couldn't screw the one in the top-left corner in (it wouldn't be secure, and I knew it would be bad if it comes off, so I didn't put the screw in). I think I read on the internet that it's okay to not install all of the screws.