Here's how to either prevent your videos from autoplaying inside of your funnels or to turn on autoplay for your videos inside of your funnel.
This is a per video basis, so go to the page on your funnel that you want to change that has the video, and click on it.
Scroll down to Playback Controls.
Find Auto Play, and if the button is on the right and shows a blue background, auto play is enabled.
Click Save and Publish located at the upper right corner.
On the other hand, to disable auto play, click the same button until it's on the left, and its background is not blue.