  We present 3D velocity measurements and acceleration limits for stars within
a few parsec of the Galactic Center (GC) black hole, Sgr A*, based on
observations of 43 and 86 GHz circumstellar maser emission. Observations were
taken with the Very Large Array (VLA) in 2013, 2014, and 2020 and with the
Atacama Large Millimeter/submillimeter Array (ALMA) in 2015 and 2017. We detect
28 masers in total, of which four are new detections. Combining these data with
extant maser astrometry, we calculate stellar proper motions and accelerations
with uncertainties as low as ~10 $\mu$as yr$^{-1}$ and 0.5 $\mu$as yr$^{-2}$,
respectively, corresponding to approximately 0.5 km s$^{-1}$ and 0.04 km
s$^{-1}$ yr$^{-1}$ at a distance of 8 kpc. We measure radial velocities from
maser spectra with ~0.5 km s$^{-1}$ uncertainties, though the precision and
accuracy of such measurements for deducing the underlying stellar velocities
are limited by the complex spectral profiles of some masers. We therefore
measure radial acceleration limits with typical uncertainties of ~0.1 km
s$^{-1}$ yr$^{-1}$. We analyze the resulting 3D velocities and accelerations
with respect to expected motions resulting from models of the mass distribution
in the GC.
