Gas forced hot air. The floor registers are hot to the touch after 6 minutes heat running, if left hand on register would burn quickly. Don't remember it being this hot before.
I find the furnace filter is very dirty or someone installed a HEPA style that creates too much back pressure reducing the air flow. Some systems do get quite warm, if your system has the correct / clean filter the fan motor bearings may need some lube this is the other thing that can reduce the air flow if a direct drive fan or a loose belt, but most of the time I have found filters that had not been changed.