What the OP refers to as gravity is at the quantum level supposed to be a scalar quantum interaction that first resolve as quantum space-time, it was the strongest force in the early universe because it was the only force. At one point in the universe energy poured into an inflating universe the same way dark energy pours in today. The only difference is that today there are photon emmitting massive reference points and in the early universe, shrouded by the CMBR, there are no such points because the compact universe was too energetic.
What needs to be appreciated here is that the early universe was a quantum state, superposition, it gets hairy because in that state all energy is supposed to be in a quantum space time unit, but as would other wise be known a point with infinite energy density. The collapse of this state is inflation which leads to quantum space-time that becomes classic space-time as observed. According to the model, energy subsequently pours into the universe as exotic particles which eventually leads to the observable matter and energy today.
There are numbers of theories out there that the inflating and reduction of scalar quantum spacetime fields is responsible for our visible universe, in much the same way that we can with high enough energy, pluck out higgs fields of inreasing energy, these can then be converted to other things. But since we cannot see behind the veil of CMBR, our emperical evidence is our visible universe.
One point I should make though, light responds to the expansion of the universe it does travel through quantum space-time but as we recall light does not age, its wave length increases, it always travels at the same speed. This is our observable, we measure the propogation of fields through comoving space-time, and now we can apparently also measure space-time waves. So lets not put the cart before the horse, because fundemental to the question of what (energy) causes secondary inflation is how spacetime behaves, and as of yet we still have not 'detected' unitary interactions of quantum space-time.