What do I say about why I left my last job? after 16 years as a production planner

They always ask why I left, and I freeze. I worked as a production planner before this. I have been practising in the mirror. Do they ask follow-ups?

If a company has been in the news for layoffs, you can mention that. Often the interviewer already knows.

Practise it out loud with a friend. Mine felt natural after the third try.