Hi,
At the very beginning it starts at zero. This is the extreme case at power ON. But during normal operation it repeatedly goes into negative because of the capacitor.
One may explain this with resonance between inductance and capacitance:
If you reduce the circuit to just the inductance and capacitor ... and a switch to push energy into the system. As soon as you switch OFF ... the circuit starts ringing. Voltage as well as currents become positive and negative, repeatedly..
Energy is repeatedly pushed from capacitor to inductance and back.
* When the absolute value of the current is at it's maximum (energy is in the coil), then the absolute value of the voltage is zero (no energy in capacitor)
* When the absolute value of the voltage is at it's maximum (energy is in the capacitor), then the absolute value of the current is zero (no energy in inductor)
Klaus