I think I determined the issue, just not sure how best to fix it.  It seems the apt-get repository doesn't always work.  I noticed that when notebook fails, the init_scripts logs show a lot of 404 errors when downloading the packages.  When the workbook is successful, there are no errors and I can see the packages get installed.

I updated the runtime to 15.4 LTS and that seems to be working consistently for now, but I am a bit nervous if this issue will pop up again