Editor freezes after hitting play, but before profiler starts to run

I'm working through a GameDev.TV advanced course and when I hit play, the editor compiles the scripts, focuses on the game view/tab, but then freezes for about four seconds before I can click to move. In the video, I'm clicking back and forth when my mouse is moving left and right.

Hope that's large enough to see! This isn't really breaking anything, just annoying. "Enter Play Mode" in Project Settings fixes this issue and makes startup super quick, but that messes with my Nav Mesh in each scene so I turned it off.

Any thoughts? Thank you!