  We study transport and relaxation of spinless fermions with long-range
Coulomb interactions at high temperatures through numerical simulations of
out-of-equilibrium dynamics. We find that the transport and relaxation are
continuously slowing down for increasing coupling $V$, and that there is a
transition in the type of transport. For intermediate couplings, the system
exhibits normal diffusive transport but the time scale for the onset of that is
long. For large couplings, it exhibits subdiffusive transport, while at the
same time the relaxation time diverges exponentially with system lengths,
featuring an MBL-like phase. We attribute the slow transport to formation of
slow bound states and stable clusters of particles. For few-particle systems we
prove existence, visualize the slowness and analyze collision properties of the
bound states. For many particles at high densities there should be a hierarchy
of clusters of particles on many different length scales. We argue that at
large couplings the average maximal size of the stable clusters should scale
linearly with the length of the lattice, which is in accordance with the
MBL-like behavior.
