[2020] Blue screen after loading

If it's an empty blue screen (or mostly empty with a bit at the bottom), then it's likely a mod issue or a simulation error. We'll need to see your output log (player.log on Mac and Linux) to be able to help. This guide explains where to find it and suggests some sites to upload it to, since we can't attach files here on Steam.
https://steamcommunity.com/sharedfiles/filedetails/?id=463645931&searchtext=log

If it's a Windows blue screen with writing on it, then the best place to post is the official forums.
https://forum.paradoxplaza.com/forum/forums/support-bug-reports.879/

Does this also happen if you start a new game? Or does it only happen with a specific save?