I'm reading that Netflix has started to play ads in between episodes. It sounds like this is true for all Netflix subscribers, but this is just a trial. Here's an article on how to opt out:
https://lifehacker.com/how-to-opt-out-of-netflixs-new-ads-1828542917
https://lifehacker.com/how-to-opt-out-of-netflixs-new-ads-1828542917