Screen jumping whilst writing email text

I don’t know what has happened when writing email text on my iPhone - instead of viewing what is most recently typed, the page continually jumps back to the beginning of the email showing sender/recipient and subject details with the first two lines of the written text beneath. It happens so quickly, it’s impossible to read what is recently written. I can’t get the page to scroll down and hold. This has only begun in the last couple of weeks. I’ve taken to writing my emails in notes then using copy/paste.

iOS is up to date, and done the shut down , restart also.

I’d also love to be able to close the keyboard and editing bar to read my newly written emails.

Thanks