  An attempt is made here to revisit structure formation in a proto-stellar
cloud during the early phase of evolution. Molecular cloud subjected to a set
of various initial conditions in terms of initial temperature and amplitude of
azimuthal density perturbation is investigated numerically. Special emphasis
remained on the analysis of ring and spiral type instabilities that have shown
dependence on certain initial conditions chosen for a rotating solar mass cloud
of molecular hydrogen. Generally, a star forming hydrogen gas is considered to
be initially at 10K. We have found that a possible oscillation around this
typical value can affect the fate of a collapsing cloud in terms of its
evolving structural properties leading to proto-star formation. We explored the
initial temperature range of cloud between 8K to 12K and compared physical
properties of each within the first phase of proto-star formation. We suggest
that the spiral structures are more likely to form in strongly perturbed
molecular cores that initiate their phase of collapse from temperatures below
10K. Whereas, cores with initial temperatures above 10K develop, instead of
spiral, a ring type structure which subsequently experiences the fragmentation.
A transition from spiral to ring instability can be observed at a typical
initial temperature of 10K.
