LR Classic V10 sometimes stalls on startup

Hello folks, I'm a new user to LR, on Classic V10, Windows10.  My issue is that the program sometimes starts up normally within a few seconds, and sometimes starts up, then immediately stalls for 3 to 5 minutes before it's possible for me to do anything with it.  During these stall periods, the line right at the top of my screen says LR is not responding, and the little blue circle (I suppose meaning 'wait') is spinning.  Other programs can start up and operate normally during this LR stall period.  Task manager tells me LR is indeed using memory, over 600mb.  I fired LR up 5 times in a row today, and twice it stalled, the first time for 3 minutes, the second time for 8 minutes.  I have only 229 photos in my catalog at this time, although there are several thousand other photos on my hard drives that LR doesn't know about.  So what could LR possibly be doing during these 'stall' periods?  Is it scanning through my drives looking for something?  When it finally comes back to life all functions seem to work normally.  The wait time is annoying, but never knowing if the startup will happen properly is even more annoying.  Any ideas?