The problem with your question is that the word energy is poorly defined. People tend to use it in a somewhat vague sense of not meaning matter, but this isn't a useful definition. For example, would you say photons were energy? If so, you would be at variance with most physicists who regard them as just another massless field along with e.g. gluons. In fact at times earlier than the electro-weak transition all particles were massless. However we wouldn't say that all the particles had become energy.
Using experimentally tested theories (i.e. the standard model) we can only go back as far as the electroweak epoch. During this period the same particles we see around us today were present, though the photon and weak gauge bosons had mixed to become electroweak gauge bosons. During this period all particles were massless. Working back in time there may be transitions due to supersymmetry breaking, unification with the strong force and eventually unification with gravity, but we have no universally accepted theories of these. However we expect that there would still be fields correspond to what we think of as particles, right up to possible transition to string theory. At no point would we describe the universe as just being energy.