macbook Pro suddenly shut down and is wanting to reinstall macOS

That’s usually a symptom of a bad corruption, or of a hardware failure. You can try the re-install, but you’ll want to get a backup copy of your storage if you don’t have a current one. Disk Utility in Recovery can get a copy to external storage, if that’ll boot and run. I’d prioritize the backup ahead of diagnostics and re-installs and repairs, if you don’t already have a copy. If this is a failing hard disk, you might only have a limited window to recover what you can get copied, a d repairs and reinstalls and diagnostics might deplete that.