  The Langevin dynamics of a self - interacting chain embedded in a quenched
random medium is investigated by making use of the generating functional method
and one - loop (Hartree) approximation. We have shown how this intrinsic
disorder causes different dynamical regimes. Namely, within the Rouse
characteristic time interval the anomalous diffusion shows up. The
corresponding subdiffusional dynamical exponents have been explicitly
calculated and thoroughly discussed. For the larger time interval the disorder
drives the center of mass of the chain to a trap or frozen state provided that
the Harris parameter, $(\Delta/b^d) N^{2 - \nu d} \ge 1$, where $\Delta$ is a
disorder strength, $b$ is a Kuhnian segment length, $N$ is a chain length and
$\nu$ is the Flory exponent. We have derived the general equation for the non -
ergodicity function $f(p)$ which characterizes the amplitude of frozen Rouse
modes with an index $p = 2\pi j/N$. The numerical solution of this equation has
been implemented and shown that the different Rouse modes freeze up at the same
critical disorder strength $\Delta_c \sim N^{-\gamma}$ where the exponent
$\gamma \approx 0.25$ and does not depend from the solvent quality.
