This work presents Relaxation-Driven Cyclic Cosmology (RDCC), a minimal, nonsingular, eternally cyclic cosmological framework formulated entirely within standard Einstein gravity coupled to a single complex scalar field. The theory is globally CPT-symmetric and fundamentally timeless: time, entropy production, and causal structure emerge only as sectoral thermodynamic projections of an underlying CPT-invariant spacetime. RDCC provides a unified explanation of dark energy (as vacuum relaxation with w>−1w > -1w>−1), dark matter (as CPT-conjugate mirror-sector baryons), baryon asymmetry, the cosmological arrow of time, and the absence of an initial singularity. A nonsingular cosmological bounce arises dynamically as a CPT fixpoint, while gravitationally mediated cross-sector relaxation prevents secular entropy growth and ensures long-term cyclic stability. The framework requires neither inflation, modified gravity, nor additional degrees of freedom. It yields concrete, falsifiable predictions, including characteristic gravitational-wave signatures, 21-cm signal modulations, deviations in ΔNeff\Delta N_{\rm eff}ΔNeff, and correlated late-time cosmological effects. RDCC is presented as a self-contained, testable alternative to the standard Λ\LambdaΛCDM paradigm. Related documents and the full RDCC ecosystem are available via Zenodo:https://zenodo.org/records/18204087 Michael Lehmannmi.lehmann@gmx.de