@DudeNamedWillare you pressing the Play button on your Home Screen? It's more likely to do that if you use that option. Instead, try going to your saves menu and selecting Load. I find that's better for avoiding it unpausing and starting off on it's own.
That's the only time it's happening to me anyway.
To try and help the long loading screens and any lagging, check your Sim total in Game Options to make sure you're not near or over the limit for your maximum Sims recommended. You can move Sims to Other Households and free up space. Check your library isn't extremely full and trim it down if it is and do the same with Other Households townies/NPCs. Clearing Library content that arrives with updates and new content can help if it's not needed in your game. When I save a room to the Gallery for example, I delete my Library copy. I keep my Other Households under about 100 or my game becomes slow and unstable. I delete NPCs from OH about once a week. Importantly, always clear personal and household inventories before switching households. This includes emptying fridges too. Carrying multiple inventories can really slow down your game.
Hope this helps!
