If you've already moved your mods folder to the desktop, delete the game cache and localthumbnail.package from the Sims 4 folder. These need to be done together.
Create a new game without any mods/cc to see if you can recreate the issue.
If the game runs well without the mods folder. This most likely means that it is an outdated mod. This can happen as we get updates for the games, some mods and custom content become outdated. You'll need to to go through your mods folder to find what needs to be replaced.
Finding Problem Mods and CC
I have been having the same problem too, but in my case, when I check which mods i've downloaded before the problem started to occur i take them out and the game still doesn't load up. I experimented with it and only put one mod that worked before the problem occurred and took out all of the other mods i had but it just won't work anymore, even with the trusted mod. Is there any solution you may know?
The mod conflict detector by DmitriMalfatto on mod the Sims might help it scans all the mods and tells you which ones are conflicting. I had downloaded some more mods and I thought they were the conflict but turns out it was just one that I already had that was broken by the patch.
I saw your text saying to put each single mod back into the game. It sounds like great idea but........ I have over 400 mods and cc, I was wondering if there was some way i could do the process faster, it has been going on for 3 days now and i feel like installing more mods but not until I find the bad mod and remove it. Please try and think of a solution!!!!
My problem : I try to open my game as usual and it is not as flexible as it normally is, it tries to laugh for about 3-5 seconds and then cuts out and it opens origin even if origin is open ! just wondering f you have seen a case like mine and if you could help.
I got 40 new custom content 3 days ago (when it started playing up) just wondering if there was a way to locate those new mods
Please reply ASAP and try your hardest to help, i have tried everything :/
Here's a list that can help you along: http://forums.thesims.com/en_US/discussion/941998/broken-updated-mods-seasons-june-2018-patch
Also, most cc is fine so start with your actual gameplay altering mods (and not clothing, hair, etc)
If that still doesn't help, use the 50/50 method: http://modthesims.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content
I don't work or have any association with EA. I give advice to the best of my knowledge and cannot be held responsible for any damage done to your computer/game. Questions belong in the forums. I don't answer questions via PM.