Strange Shadows popping in (Cycles)

I’m new to Blender and 3D Modeling and Animation.
I’ve got a lighting problem, around 5sec into the video some wrong looking shadows popping into the rendered frames.
My lightsource is a Sun.
Does anyone know what could cause this?
Sadly, i can’t upload files because i’m new to this community.
Link to the Video: https://www.youtube.com/watch?v=Wzct85y_6fM&feature=youtu.be

First off, welcome to the community, @Len105! It is really hard to tell exactly what is happening, but answering some questions could lead us in the right direction. Did you render to images before encoding your video (if you did not, here is a great personal example of why you almost always should render to images first)? If you did, you can use a file browser to find out which frame the shadows appear at. This will make it easier to analyze your model/scene for possible causes. When you find out which frame, scrub to that frame in the timeline and look for any possible causes - maybe a greeble got accidentally keyframed. Maybe there’s some sort of keyframed material property.

Take a look at that to see if it is an easy fix, otherwise, it is actually pretty easy to move up in user class in the forum - I think it just takes viewing a few threads and making a few replies (I can’t find the exact numbers at the moment). That’ll get you the class upgrade that allows you to upload files.

Thanks for your answer.
I did render it as individual images and i know at which frame they appear. I will check the project later, maybe i can finde the issue.