LR classic 10.1 freezes _after_ startup for about 10-15 seconds

[nu-b]

This started happening with LR classic 10.1 on Windows.  Does not happen with 10.0, so I've downgraded back to that version.

LR (10.1) starts up normally and runs fine for about 15-20 seconds.  Then it completely freezes for about 10-15 seconds.  After that it's fine.  During the freeze, CPU usage is way up, but it appears the GPU is not being used.  This happens every time I start it in 10.1, single or dual monitors, GPU turned on or off.

System: two 4K monitors, Intel i9 9900K, 32gb RAM, GeForce RTX 2070 super.  Program, catalog, images and cache are all on NVMe drives.

[GoldingD]

Where is the catalog located?

[nu-b]

System has teo NVMe drives.  Catalog/images are on one; program and camera raw cache are on the other.  I've been using this setup for nearly two years, and the problem occurs only with LR 10.1.