  A Friedman cosmology is investigated based on scalar-tensor gravitation with
general metric coupling and scalar potential functions. We show that for a
broad class of such functions, the scalar field can be dynamically trapped
using a recently suggested mechanism. The trapped scalar can drive inflation
and accelerated cosmic expansion, compatible with standard requirements. The
inflationary phase admits a natural exit with a value of the Hubble parameter
dictated by the duration of inflation in a parameter independent manner. For
inflationary duration consistent with the GUT description, the resulting Hubble
parameter is found to be consistent with its observed value.
