My house has a Friedrich brand furnace about 25 years old or so.
Sometimes I run the blower continuously (that is, not under control of
the thermostat) just to keep the air circulating in the house--neither
heating nor cooling active. Recently the blower motor has been cutting
out. The motor will just stop for several seconds and then restart
itself. Since this is probably not good for the motor, I have stopped
running the blower continuously.

Just wondering if there are is a typical cause for this. Do I need a
whole new blower or can I easily repair this motor by installing new
brushes or some such thing?

Thanks for any input.