A pattern interrupt is any change in the visual or auditory experience that re-engages the viewer's brain. This can be a text overlay, a zoom-in, a sound effect, or a b-roll clip.
Avoid the very beginning. Instead, place one at roughly 30% through the video after you have provided initial value, and another at 80% before the final summary.
Start with the end result first or present a high-stakes question. Eliminate any "Hey guys, welcome back" fluff and get straight to the value within 3 seconds.