Sims 4 Screen Flashing White on Startup

JasminCrown  Please try playing with no mods or custom content, as in, move the Mods folder to the desktop and delete localthumbcache.package.  You don't need to save your progress; this is just for testing.  It's important though to find out whether the issue is due to something in your Mods folder.

If that doesn't help, please provide a dxdiag.  Hit Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop.  From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.

Also, I did the first option you suggested just to make sure and it is a mods issue. The problem is just figuring out what it is.

JasminCrown  If you have a lot of mods to sort through, the 50/50 method can make the process much more efficient:

https://modthesims.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content#The_50.25_Method

JasminCrown There Broken/Updated Mods list has now moved here. See Broken/Updated Mods & CC 1.112 . 

Thanks for the reply’s, I looked at all of this and followed suit. Also, I’ve organized my mods folder and have been putting folders in one by one. The problem now is, I’ll put a folder in, test it and have no white screen and then I’ll test again and it’ll flash a white screen. So now I don’t know what is causing it. I’ve been trying to fix this for two weeks, and I’m so close to giving up. 

Are you saying that without making any change to your Mods folder it will sometimes flash white and sometimes not? If you play with no mods more than one time or for a while, does the flashing start again?