so, about 440 grit? (per internet)
that's still really fine.
is the paper getting clogged with oil and dust pretty quickly?
when it starts to get clogged with paint is when the heat starts to build.
only solutions I can think of is a much coarser paper, much drier paint (like days/weeks from now, or a heat gun for a day), or change to fresh paper every time it starts getting clogged (which would be very very often, at this point).
one other thing . . . well two: don't sand one area repeatedly (repeated strokes), move around in large random circles (so heat doesn't start building . . . by the way, heat makes clogging happen faster too, with oil involved)
and you could use some kind of lubricant ("wet" sand . .. with oil, solvent, water, soapy water, whatever the media can handle) . . . although I imagine wet sanding isn't really an option here