Well, computers are not TV’s and you don’t have remote controllers to shut them down while lying in your bed.
The idea is how to make our computer to automatically shutdown after watching a movie. There are many free media players which can do this. But from my experience I would recommend you Media Player Classic Home Cinema, also called MPC-HC.
I would recommend you to install K-Lite Code Pack where in the process of installation you will have to check to use Media Player Classic.
Then you will open your favorite movie and from the menu, Play -> After Playback, you choose Shutdown.
Now you can lie in your bed and watch the movie without having after to stand up and turn off your computer. When the movie will finish the playback will give the Shutdown command to your computer. So you will not have to do it manually.