Hello 
May I ask if your are flying an IniBuilds aircraft, like a320/a330/a400m ?
What you describe might loooks like this, but it’s not really a CTD, just a complete freeze : Sim freezes when returning to main menu with inibuilds aircraft - #173 by Marklar666
If not, you confirm that you have a CTD (Crash To Desktop, with MSFS closing without your intervention) ?