  We use Keck/HIRES spectra of 37 optically bright quasars at z=2-4 to study
narrow absorption lines that are intrinsic to the quasars (intrinsic NALs,
produced in gas that is physically associated with the quasar central engine).
We identify 150 NAL systems, that contain 124 C IV, 12 N V, and 50 Si IV
doublets, of which 18 are associated systems (within 5,000 km/s of the quasar
redshift). We use partial coverage analysis to separate intrinsic NALs from
NALs produced in cosmologically intervening structures. We find 39 candidate
intrinsic systems, (28 reliable determinations and 11 that are possibly
intrinsic). We estimate that 10-17% of C IV systems at blueshifts of
5,000-70,000 km/s relative to quasars are intrinsic. At least 32% of quasars
contain one or more intrinsic C IV NALs. Considering N V and Si IV doublets
showing partial coverage as well, at least 50% of quasars host intrinsic NALs.
This result constrains the solid angle subtended by the absorbers to the
background source(s). We identify two families of intrinsic NAL systems, those
with strong N V absorption, and those with negligible absorption in N V, but
with partial coverage in the C IV doublet. We discuss the idea that these two
families represent different regions or conditions in accretion disk winds. Of
the 26 intrinsic C IV NAL systems, 13 have detectable low-ionization absorption
lines at similar velocities, suggesting that these are two-phase structures in
the wind rather than absorbers in the host galaxy. We also compare possible
models for quasar outflows, including radiatively accelerated disk-driven
winds, magnetocentrifugally accelerated winds, and pressure-driven winds, and
we discuss ways of distinguishing between these models observationally.
