In nonpolar polymers, positronium (Ps) is dominantly formed by fast intraspur reactions of the energetic positron, but its formation is partially contributed by recombination of weakly bound Mott-Wannier-like positron-electron pairs and is susceptible to electric field and positron irradiation induced perturbations. The average initial energy of para-Ps (p-Ps) formed by recombination is found to be about half the energy of ordinary p-Ps dominantly formed by the fast intraspur reactions.