First it takes a minute showing this message in the console
Read prefs: C:\Users\thinsoldier\AppData\Roaming\Blender Foundation\Blender\2.91\config\userpref.blend
WARN (bke.anim_sys): C:\b\buildbot-worker-windows\windows_291\blender.git\source\blender\blenkernel\intern\anim_sys.c:2926 BKE_animsys_eval_driver: invalid driver - cycles.preview_denoising_start_sample
then it says it found python and then waits another minute
then it MAYBE will open the main Blender window and let me use it.
I updated to the latest nvidia studio drivers and now the problem happens in both 2.91 and 2.90. It did not used to happen in 2.90.
Now both 2.90 and 2.91 eventually open consistently but when I try to render with cycles they freeze and I have to force quit them.