Screen blurs when I try to record videos on iPhone
First, have you force quit the camera app and restarted your phone?

This could be one of two things both are prompted by the Camera app being unable to start the camera properly.

The first is that the physical camera isn't working some or all of the time, depending on the phone model it might be that one of the back cameras works but not the front. This would be verified by either trying to film using the front camera, or use the back camera in photo mode.

If all the cameras work in the photo mode then you should move on to trying to reinstall the operating system:


Take a backup using iTunes/Finder or iCloud, ensure it is fully backed up, all options are enabled.
Erase the iPhone using the Erase all content and settings feature.
Setup the iPhone as a new iPhone, ignore the backup for now.
Test the camera.


If the camera is still not working you need to seek a repair from Apple.

If the camera is working, erase the phone again this time try restoring the backup. If the issue returns then you will need to copy all of your settings off the phone as there is no further action that can be taken beyond simply starting the phone from blank again. Obviously you can sync all your settings with iCloud but you will need to essentially set it up from new.