Working with styles?
Which version of InDesign?!
(And why the pasting from Notepad by the way...?)
Complete noob - no styles, most up-to-date version I think 11.1.0
Notepad because last year's document is only available in PDF, and I ran the text through Notepad in case it needed cleaning of any crap, the way Word used to ...
This has nothing to do with the use of styles, or Notepad. We've seen similar reports related to CC Libraries.
Are you using TypeKit fonts or CC libraries, or anything else that might want to have an internet connection? Are you connected?
Does it happen in a different Windows user account? If you start in Safe Mode?
Gentlemen - thanks for your interest - the problem was solved by creating a new document and pasting the text into it. Something wrong with the old document, clearly. Many thanks