Restart countdown for each scene within one video?

Howdy. I have a long video with different scenes/speakers. I’d like the countdown to be set per scene, and then when the next scene/speaker starts, the countdown resets, as a way to keep people engaged (example https://www.facebook.com/GoodMythicalMorning/videos/859311101076338/) 
I just signed up assuming I could manually adjust the countdown timers, but I’m not sure now. Please let me know if this is possible. Thanks!