So I was trying to make a "regulator" and I noticed it seemed to start-up nicely as well.
The trick is to use one of the feedback signals to generate a down pulse through a dumb charge pump. The P MOSFET conducts for a while (see the lower trace) and the potentiometer handles the RC constant. Apparently 100K and 100nF are about good for a sustained oscillation, but higher voltages can be reached very easily with more than 200K.
The period is still determined by the tank capacitor.
The 1G resistor is here for stability of the simulation, it's purely symbolic and otherwise useless...