In a steady state, L2 is a short, so Vb(Q2) is V1 / 2 because of the R1/R2 divider. This is enough to keep Q2 open, but that also opens Q1, which tries to pull Vb(Q2) to ground, but L resists this change, creating delay. Eventually Q2 will close, which will close Q1, and R1+R2 will start charging the inductor, which it will also resist. But eventually Vb(Q2) will rise again, and the cycle repeats.
Attached is a bit easier to read version of the schematic.