  IGR J16320-4751 is a highly obscured HMXB source containing a very slow
neutron star ($P_{spin}\sim1300$ sec) orbiting its supergiant companion star
with a period of $\sim$9 days. It shows high column density
($N_{H}\sim2-5\times10^{23}$ $cm^{-2}$) in the spectrum, and a large variation
in flux along the orbit despite not being an eclipsing source. We report on
some peculiar timing and spectral features from archival XMM-Newton observation
of this source including 8 observations taken during a single orbit. The pulsar
shows large timing variability in terms of average count rate from different
observations, flaring activity, sudden changes in count rate, cessation of
pulsation, and variable pulse profile even from observations taken a few days
apart. We note that IGR J16320-4751 is among a small number of sources for
which this temporary cessation of pulsation in the light curve has been
observed. A time-resolved spectral analysis around the segment of missing pulse
shows that variable absorption is deriving such behavior in this source. Energy
resolved pulse profiles in the 6.2-6.6 keV band which has a partial
contribution from Fe K$_\alpha$ photons, show strong pulsation. However, a more
systematic analysis reveals a flat pulse profile from the contribution of Fe
K$_\alpha$ photons in this band implying a symmetric distribution for the
material responsible for this emission. Soft excess emission below 3 keV is
seen in 6 out of 11 spectra of XMM-Newton observations.
