After checking the replies, I pulled the panel on the furnace to inspect
the motor area. Much to my surprise, the filter was more clogged than I
had expected. It seems it wasn't that long ago that I changed the filter
but I guess it was longer than that. Anyway, I installed a fresh filter,
turned on the blower, and it has not cut out since then. So I guess the
clogged filter was causing the motor to overheat. But I have been in
this house for 10 years and this has never happened to the motor before.
I've never exactly been religious about changing the filters but I've
always changed them several times a year. I guess this is my wake up
call from an aging system--better be more disciplined about changing
those filters. The A/C components are even older--somewhere between
25-40 yrs. Just trying to delay the inevitable...

thanks all