No, not without some really contrived circumstances
To evolve three heads, Cerberus would need to evolve, for a long time, in a niche where it's better to have three sets of eyes, noses, teeth and brains than a single set of highly adapted eyes, nose and teeth. Let us note that evolution doesn't usually just sprout a new feature to achieve a given purpose, it starts with an existing anatomical feature then molds into the ideal shape for a given niche. Two extra heads with duplicated skulls of the first head is highly redundant. Practically everything you'd expect from three heads can be achieved more cheaply with a specialized single organ. Need to see in 360 degrees? Get chameleon eyes. Hear behind you? Articulated ears. Need to eat quickly? Get a giant mouth with lots of teeth.
I can't think of a set of circumstances where it's a clear and long standing advantage to have three heads instead of just one. There are real costs to metabolism, neurological complexity and over-all competitiveness that come with three heads compared to a single head.
Now, if you have a magic gene splicer and nursery, anything is possible...but that's not typical evolution either.