  Changing-look phenomenon observed now in a growing number of active galaxies
challenges our understanding of the accretion process close to a black hole. We
propose a simple explanation for the sources where multiple semi-periodic
outbursts are observed, and the sources are operating at a few per cent of the
Eddington limit. The outburst are caused by the radiation pressure instability
operating in the narrow ring between the standard gas-dominated outer disk and
the hot optically thin inner Advection-Dominated Accretion Flow. The
corresponding limit cycle is responsible for periodic outbursts, and the
timescales are much shorter than the standard viscous timescale due to the
narrowness of the unstable radial zone. Our toy model gives quantitative
predictions and works well for multiple outbursts like those observed in NGC
1566, NGC 4151, NGC 5548 and GSN 069, although the shapes of the outbursts are
not yet well modeled, and further development of the model is necessary.
