@SneezySpice
When loading worlds in Live Mode all of your active content is loaded, including all clothing items which are worn by the sims which are active on the lot to be loaded. This is very demanding of all components of your computer, especially your hard drive controller(s) and memory. Large numbers of files will reduce the performance of your drive controller and CPU while large collections of high resolution content will fully utilize the memory bus of your display adapter (video card) while the world is being loaded. The Sims 4, as all versions of the sims have been, is very demanding of system memory due to it's nature therefore it is recommended that you ensure your system meets the standard for the current generation of high definition videogames. If you believe that your system meets or exceeds the standard then we will require the results of your system diagnostics, to confirm that you are running the '64-bit' version of the game, and that your graphic drivers are current.