Well keep your Macbook closed when watching TV! Only kidding, I'm exactly the same. it sounds like something either to do with WiFi (because when you switch your Macbook on, one of the first things it does it connect to WiFi), Airplay or home sharing.
It's a bit trial and error but you can narrow it down by trying the following:
- Use a wired connection for Apple TV (if possible) and see if the same problem occurs when you open your Macbook
- Try switching off WiFi on your Macbook, closing it, switching Netflix on and then try opening your Macbook
- Try using Airplay on Macbook and see if that works ok on Apple TV
- Try switching off Airplay on your Macbook and see if that works
- Make sure Apple TV has latest software
- Does the same thing happen with other WiFi devices (computer, iPhone, iPad etc)?
- Switch off home sharing and/or close iTunes and try Netflix then.
You should be able to identify the problem depending on what happens on the scenarios above. It could something as simple as changing WiFi channel or switching off something in settings. I have two Apple TVs (one wired and one wireless) and a Macbook and I don't experience any problems with Netflix.