It's also running W7 so that may be a clue that it's just another old PC. The usual fix is a new motherboard but I try to avoid that with the following steps.

No, I will not open a debate about Windows 7.

1. Pull the old HDD out, slip in a blank SSD.
2. While the machine is open, clean the heatsinks, do a fan check and reseat all sticks, cards and cables.
3. Update the BIOS. Reset the BIOS to default and change only what is needed for step 4.
4. Install W10. no activation needed as this is a test run.
5. Install drivers and apps specific to this build.

Now test.