If that video is with the Mac running on battery and not plugged in, you may have an old battery problem, especially if that is the original battery. Do you know how many battery cycles you have?
1) Plug the Mac in
2) Click on the Apple icon in the top left corner
3) Click "About this Mac"
4) Click System Report
5) Click on the Power Option from the list
6) Look Under Heath Information
7) Cycle Count