From the Wikipedia entry on Betelgeuse: "Some theorists[who?] have speculated that this behavior is expected for a star at the beginning of the gravitational co

From the Wikipedia entry on Betelgeuse: "Some theorists[who?] have speculated that this behavior is expected for a star at the beginning of the gravitational collapse at the end of its life.[citation needed] The mass of Betelgeuse puts it in range to become a neutron star or possibly a black hole." So this might be what is happening. .