Faulty Heater Blower - 2001 525d Touring

My heater blower has failed so neither the heater or aircon work. The
control panel is the basic model with knobs rather than the more
sophisticated electronic climate control unit.

The blower seems to be dead, although very occasionally it will run
briefly (for half minute or so) before shutting off. The intermittent
nature of the problem leads me to think that the snag could be a loose
connection, bad thermostat or faulty control of some sort.

I'm no expert, but if someone could offer me simple advice I would be
most grateful.

Paul