What you are seeing is shimmering caused by Anti-Aliasing. It is usually caused by reflections and lighting. You can adjust this by adding a Post Process volume to the level and changing the AA Method.
If this doesn’t help, feel free to post your dxdiag and we can take a look at your specs.
What you are seeing is the slight bumpy variations in the normal map channel of that floor material. Here is a very smooth reflective material in comparison.