The only thing that seems to work for me, right now, is to force quit the game (you have to wait until it is completely closed and no longer shows the quit option in the console menu), then delete reserved data and re-open the game. It's exhausting to do, especially for months on end. I'm not comfortable even deleting the reserved data, personally.
It started happening to me when they began doing the Sims deliveries. I can never download them because they cause the console to say the game took too long to start, and deleting the reserved space removes the downloaded content. That's how I figured out it was the problem. No troubleshooting advice ever works for me aside from deleting that data.
Xbox says it's not the console having problems, and it only happens with Sims, so we're all basically stuck waiting for EA to fix it ☹️