Have you downloaded anything recently ?
Can you right click on the taskbar and select Task Manager.
If this will be the first time you have accessed Task Manager, you will be presented with a blank window - just click on More details bottom left.
Under Processes check to see if anything is hogging the CPU.
Clicking on CPU will sort to highest user first.
Under Start-up will show if any of your start up items have a high impact.
If there's nothing obvious, click on File/Exit then go Start -type %temp% and press enter when it comes up.
If that is highly populated then press CTRL a to highlight then CTRL d to delete.
Confirm then check the box and select Skip - you may need to empty the recycle bin afterwards.
I've just checked my other Win 10 laptop (1809) and I don't get a log in screen whether I use Windows or the program to boot into Safe Mode with Networking.
I used to when booting into that mode through Windows, but I would have to check this 1803 machine later to see if I still get it.