Imported video pausing at beginning when export presentation as video

[dunnster]

I have a presentation that has a few .mp4 videos that play automatically on the timeline. When export my complete presentation as a .mp4 format the inserted video's pause at the start and display the buffer icon just for a couple of seconds before playing correctly.

Any ideas on why this could be happening?

[Lilybiri]

Because it takes time to load the video file, which can be huge. 

Do not start with a video lside, start with a static slide. Keep the videos as small as possible, eventually distribute them over different slides.