So this has been happening to my iPhone 7 lately where the video mode is really blurry and keeps blinking as if it’s trying to turn on and doesn’t quite make it there. Thought it was maybe a hardware issue or possibly damage from peeking at the latest solar eclipse.  It’s neither of those things though.  After some google searching, people are powering down the phone, resetting the phone, switching to photo mode and then back to video.  What has worked for me was closing all open apps and today I figured out that the photos app when closed stops this loop from happening. So, if this ever happens to you, try this:

double tap the home button

find the photos app

swipe up

that’s it. Annoying, at least it’s not that hard to do.  Good luck!