Would you start any treatment for radiation pneumonitis if there is a large area of consolidation in the irradiated lung field but the patient is asymptomatic?

If the timeline matches then for radio graphic only pneumonitis, I would favor observation with a repeat scan in a few months.

No. For asymptomatic CT findings, I usually follow closely to ensure clinical stability and ideally radiographic resolution. Steroids have an unfavorable toxicity profile and may interfere with systemic therapies.