Autodesk recently released AutoCAD 2021 and many users have started to experience errors when launching the software again. The first launch usually goes smoothly, but the following launch prompts the "Let's Get Started" dialogue box once again.
We have found that if you do not have the Autodesk Desktop App running in the background and signed-in, this will trigger the dialogue box. Once you close AutoCAD, launch and sign-in on the Autodesk Desktop App, then relaunch AutoCAD 2021, this goes away.
We also recommend updating your licensing service to the latest hotfix - Autodesk Licensing Service - 10.1.1.66 (released March 25, 2020). You can do so through the Autodesk Desktop App. Install and it'll download for you.