I had this especially happen in Linux, after I patched or something.
I discovered when opening (something like windows task manager) that multiple battle net things were running, agent.exe, etc and what not. Closing all that junk helped.
Also:
This was going on in 2014 also 
Could you try deleting the main cache folder located in your World of Warcraft folder? If it becomes corrupted, it can cause the crash you’re seeing. It’ll be rebuilt by the game as you play.