  We study the multifield dynamics of axion models nonminimally coupled to
gravity. As usual, we consider a canonical $U(1)$ symmetry-breaking model in
which the axion is the phase of a complex scalar field. If the complex scalar
field has a nonminimal coupling to gravity, then the (oft-forgotten) radial
component can drive a phase of inflation prior to an inflationary phase driven
by the axion field. In this setup, the mass of the axion field is dependent on
the radial field because of the nonminimal coupling, and the axion remains
extremely light during the phase of radial inflation. As the radial field
approaches the minimum of its potential, there is a transition to a second
phase of inflation during which the axion field contributes a substantial
fraction of the system's total energy density, yielding a phase of "natural
inflation." This system exhibits ultra-light isocurvature perturbations, which
are converted to adiabatic perturbations by a turning field-space trajectory.
For models wherein the CMB pivot scale exited the horizon well before the turn,
this acts to suppress the tensor-to-scalar ratio $r$, without generating CMB
non-Gaussianity or observable isocurvature perturbations. Finally, we note that
for certain parameters the interaction strength between axion and gauge fields
can be suppressed during the first phase of inflation relative to its value
during the second phase by several orders of magnitude. This decouples the
constraints on the inflationary production of gauge fields (e.g., from
primordial black holes) from the constraints on their production during
(p)reheating.
