If a bunch of particles were floating in empty space with no external forces acting upon them, they would not be gradually drawn towards each other by the force of gravity. The reason is that gravity is an attractive force between masses, but for particles to be drawn towards each other, there must be an initial non-zero net gravitational force acting on them.
In a homogenous distribution of particles with no initial deviations or variations in mass density, the net gravitational force on each particle would be balanced from all directions. This is known as gravitational equilibrium. Consequently, the particles would remain in their respective positions without any tendency to cluster or coalesce.
The concept you mentioned regarding the second law of thermodynamics is related to the increase of entropy or disorder in a closed system. However, in this scenario, since there are no energy transfers or interactions, the second law of thermodynamics does not directly apply. The absence of an initial gradient or non-equilibrium state means that the particles would not spontaneously cluster due to gravity alone.
It's important to note that on cosmological scales, gravity does play a significant role in the formation of structures like galaxies, stars, and planets. But these structures form from initial inhomogeneities and fluctuations in the distribution of matter and energy in the early universe, not from a uniform and homogeneous distribution of particles.