We condensed our data file and followed all the recommendations by QB.  The Start-up of QB is still slow as a snail, and it's random as well.  Never had this issue with the past versions.  It's not our operating system.  It's not other programs running the background.   Ideally, we'd prefer to run QB 2017, But...... ya can't do that.  Once you install QB2020 it "updates" your data file and you can't use it on previous versions. 

 And, since we have a Payroll subscription with Intuit we have to use 2020.  What Intuit does to generate additional revenues is they force you to update to a new QB version every 3 years if you have their payroll subscription.  

Intuit is not a great company it once was.  Its exclusively driven by revenues; short-sighted.  No vision.