Ok, first of all save your entire Sims 4 folder to either an external hard drive or USB thumb drive. This is to insure your saved games are safe. You should periodically save your games to one of these to prevent headaches if something happens to your game.
Next move the entire Sims 4 folder to your Desktop and DO NOT DELETE IT! This is where your CC/Mods and saved games are stored.
Start up Sims 4 as normal remembering that none of your CC/Mods or saved games will appear. Also, turn off Automatic Updates. Start a new game, play for about an hour or so and then save and exit the game. If the game saves and quits as normal, then it is probably one of your Mods or CC that is causing the issue.
Please note that anytime a new patch or new content is released, Mod and CC creators must update their content to be compatible. Quite often a new patch will change the way something works. This is why you turn off Automatic Updates to insure that you can then apply the patch once your favorite Mods/CC is updated, but in the meantime you can still play. EA/Maxis does not support these Mods and any further issues with them must be addressed by the creator.