  The Raman peak position and linewidth provide insight into phonon
anharmonicity and electron-phonon interactions (EPI) in materials. For
monolayer graphene, prior first-principles calculations have yielded decreasing
linewidth with increasing temperature, which is opposite to measurement
results. Here, we explicitly consider four-phonon anharmonicity, phonon
renormalization, and electron-phonon coupling, and find all to be important to
successfully explain both the $G$ peak frequency shift and linewidths in our
suspended graphene sample at a wide temperature range. Four-phonon scattering
contributes a prominent linewidth that increases with temperature, while
temperature dependence from EPI is found to be reversed above a doping
threshold ($\hbar\omega_G/2$, with $\omega_G$ being the frequency of the $G$
phonon).
