The paper investigates a novel reheating scenario where the inflaton φ oscillates around the minimum of a monomial potential \( V(\phi) \propto \phi^n \) with \( n > 2 \). This scenario involves the annihilation of inflatons mediated by a massive scalar mediator \( S \). The dynamic evolution of the inflaton mass leads to resonance phenomena, resulting in non-trivial temperature evolution during reheating. The authors solve the coupled Boltzmann equations to present solutions for radiation and temperature, revealing that the maximum temperature during reheating can be influenced by the location of the resonance relative to the end of reheating. They also explore the impact of this resonant reheating on dark matter (DM) production, showing that the mediator can participate in both the genesis of dark matter and the standard freeze-in dynamics. Additionally, they demonstrate that next-generation gravitational wave detectors could test this scenario by observing primordial gravitational waves. The paper is organized into sections covering the introduction, post-inflationary reheating dynamics, dark matter freeze-in during resonant reheating, and gravitational production of dark matter.The paper investigates a novel reheating scenario where the inflaton φ oscillates around the minimum of a monomial potential \( V(\phi) \propto \phi^n \) with \( n > 2 \). This scenario involves the annihilation of inflatons mediated by a massive scalar mediator \( S \). The dynamic evolution of the inflaton mass leads to resonance phenomena, resulting in non-trivial temperature evolution during reheating. The authors solve the coupled Boltzmann equations to present solutions for radiation and temperature, revealing that the maximum temperature during reheating can be influenced by the location of the resonance relative to the end of reheating. They also explore the impact of this resonant reheating on dark matter (DM) production, showing that the mediator can participate in both the genesis of dark matter and the standard freeze-in dynamics. Additionally, they demonstrate that next-generation gravitational wave detectors could test this scenario by observing primordial gravitational waves. The paper is organized into sections covering the introduction, post-inflationary reheating dynamics, dark matter freeze-in during resonant reheating, and gravitational production of dark matter.