Why does my I/Q data from radar are not centered?
The IQ data from an FMCW radar would have the frequency difference from the delay between the transmitted and reflected signal given the transmitted signal is a changing frequency with time; so the result is what should be expected. Given the ramp rate of frequency the round trip delay from target can be determined from the frequency of this result.

The result here appears to have a stronger higher frequency AND lower frequency tone as the result of two different targets. The lower frequency that is superimposed would be due to the closer target.