  The multiband nature of iron pnictides gives rise to a rich
temperature-doping phase diagram of competing orders and a plethora of
collective phenomena. At low dopings, the tetragonal-to-orthorhombic structural
transition is closely followed by a spin density wave transition both being in
close proximity to the superconducting phase. A key question is the nature of
high-$T_c$ superconductivity and its relation to orbital ordering and
magnetism. Here we study the NaFe$_{1-x}$Co$_{x}$As superconductor using
polarization-resolved Raman spectroscopy. The Raman susceptibility displays
critical enhancement of non-symmetric charge fluctuations across the entire
phase diagram which are precursors to a $d$-wave Pomeranchuk instability at
temperature $\theta(\mbox{x})$. The charge fluctuations are interpreted in
terms of quadrupole inter-orbital excitations in which the electron and hole
Fermi surfaces breathe in-phase. Below $T_c$, the critical fluctuations acquire
coherence and undergo a metamorphosis into a coherent ingap mode of
extraordinary strength.
