You probably already know about the Uncertainty Principle.
For something the size of a hydrogen atom, the uncertainty of position is about 6 diameters, so it becomes problematic even at that scale to speak of something like vibration, which kind of requires some specific locations with which to describe the vibration itself (the size and limits of the wiggle)...
The strings in String Theory are very small - if you were the size of a String, the diameter of a proton next to you would be about the distance to the Andromeda Galaxy... 2.5 Million Light Years!
Strings are so small that the Uncertainty Principle and just about all of the rest of what we think we know makes all accounts of their possible behaviors totally abstract (hence the hard math)... in some respects, once you get below the size of atoms the concepts of size, shape, form, length, motion, rotation, etc. just don't have any substance to work with... at the level of the Strings, I don't know if anyone really knows what to think about them.