  The Josephson equations predict remarkable effects concerning the phase state
of a superconducting junction with an oscillating current induced by a static
voltage. Whether the paradigm can be twisted by yielding an oscillating voltage
without making use of harmonic drives is a fundamentally relevant problem yet
not fully settled. Here, we demonstrate that a dynamical regime with an
oscillating phase evolution is a general hallmark of driven Josephson systems
exhibiting sign competition in the Josephson couplings. We show that in
frustrated Josephson systems an oscillating phase dynamics gets switched on by
driving the changeover among different ground states, which can be induced by
varying the parameters that set the phase state. Remarkably, the character of
the transitions in the Josephson phase space allows different types of
dynamics, with few or several harmonics. This result sets out a characteristic
mark of any superconducting system with frustrated Josephson couplings and can
be exploited to disentangle the complexity of the underlying phases.
