Memory retraining is a process to initialize the memory module and run diagnostic tests for the memory module in your computer.
Memory module replacement
Total Memory Encryption setting change in the UEFI BIOS
Memory Reference Code (MRC) change when the UEFI BIOS updates
When memory retraining occurs, the screen might be blank. You might see the LED indicators on Esc, F1, and F4 blinking sequentially to indicate the progress. Do not press the power button to interrupt the process. Wait a few minutes until the logo screen is displayed.