Active three-dimensional (3D) microwave and millimeter-wave imaging is useful for a variety of applications including concealed weapon detection, in-wall imaging, non-destructive evaluation, and others. High-resolution imaging is usually performed using a fixed two-dimensional planar or cylindrical aperture that is defined using a two-dimensional array or precise mechanical scanning of a transceiver or sequentially-switched linear antenna array. For some applications, it is more convenient to manually translate a linear array over the scene of interest, or equivalently, move the target in front of the linear array to scan an effective aperture. Manually scanning the array or target creates several challenges for accurately focusing, or reconstructing, an image of the target. The motion of the array or target must be known accurately, typically with precision of 0.05-0.1 wavelengths. Additionally, the image reconstruction algorithm needs to be able to compensate for aperture shapes which are highly non-uniformly sampled, and which are not of a specific canonical shape such as planar or cylindrical. This paper explores high-resolution 3D microwave imaging of a moving target by using optical motion capture to track the moving target and develops highly versatile image reconstruction techniques that account for the irregular motion. Several experimental results are shown for moving targets in front of a fixed linear array.