Reinstalling the app is an option, but not the first one. If everything was working fine before and then it started freezing, it's most likely a conflict with a system update or a buildup of the app's cache. Try clearing the camera cache specifically in settings first - not everything gets deleted with a regular cleanup. You go into "Apps", find the camera, open "Storage" and clear all the cache there. Restart and try opening it.
If that doesn't help, then go ahead and reinstall the app like I mentioned above. But before that, turn off video acceleration in the camera settings if you have it on - on some Redmi Note devices this can cause lag when opening. Also check if another app isn't running in the background - like cloud sync or document scanner, they sometimes eat up resources.
If the freezing continues after all these steps - then look at the hardware side of things, could be an issue with the camera itself or its sensors. On Redmi Note 13 this happens rarely, but it's possible. You might need diagnostics at a service center.