I’ve seen this problem quite a few times (not on X5's though) and it’s usually caused by either a defect in the tyre, or tyres that don’t have very good manufacturing quality control.
Modern wheel balancing machines can achieve some amazing things in that you can balance a tyre with all sorts of issues.
One of the common problems with some cheap tyres is that many are not actually round, and while you can balance these perfectly, they cause all sorts of strange vibrations and harmonics at various speeds.
Another potential problem is that the tread may not be running true; that is, it has a wobble from side to side as the tyre rotates. Again, tyres with this problem can also be balanced but you will also suffer from odd vibrations as various speeds.

When ever you get a new set of tyres pay attention to how much weight is needed to balance each wheel. A wheel that has significantly more weight than the others sometimes indicates a manufacturing issue with the tyre.