One problem related to body has been reported for the 2006 BMW Z4. The most recently reported issues are listed below.
The convertible top on the 2006 Z4 BMW has a mechanism that raises and lowers that fails. It's location is such that it is exposed to the elements. When I bought my car (used)I went to a BMW mechanic that told me that if I did have him fix it it would happen again. Talking to other BMW mechanics I got the same info.