DC current through the bias resistor starts to turn the transistor on. the transistor pulls current through the bottom winding of the transformer, inducing a current through the primary side capacitor, pulling itself off. current in the transformer secondary winding flows into the capacitor until it stops, then starts to discharge. as it discharges through the secondary side, it induces current on the primary side, charging the capacitor on that side, sending current through the base of the transistor, turning it back on
