Memtest86+ is a small tool that allows you to test memory for issues.
1. Obtaining media
You may also use the official Memtest86+ ISO, or the install tool for Windows.
2. Creating bootable media
This will require a USB that is at least the size of the ISO you downloaded.
Follow the Linux media guide to create the install media. If you use Rufus, make sure to select MBR/Legacy/BIOS even if your system supports GPT/UEFI.
This media needs to be booted in Legacy/CSM mode. They will not work when loaded in UEFI mode If you used the official Memtest86+ media, it will boot straight into the test.
Let the test run for 8 passes, which will most likely last overnight. Any errors means you have a bad RAM stick or DIMM (RAM slot). If you see any errors early, you can end the test there and start narrowing it down to which stick/slot.
If you have a failure, then test each stick individually, and in different slots to isolate the failure to a stick or slot.