There is hardly a painter alive who hasn't, at one time or another, attempted at least ONE self-portrait. As near as I can recall, I've done about five or six, the earliest being when I was about 14. The most recent one wasn't a painting but a colored pencil drawing done about three years ago. Sometimes artists paint themselves out of ego, sometimes out of boredom, sometimes because they simply lack an affordable model. Sometimes they can be very introspective, in other cases, very superficial and pretentious. Vincent Van Gogh, of course, is famous for his self-portraits. He painted over a dozen of them. That sounds like a lot, but the average for most well-known artists over a lifetime is about that. The only difference is, Van Gogh painted that many over the course of just two or three YEARS. However, the world's champion self-portrait painter of all time was Rembrandt van Rijn.
Rembrandt, over the course of his lifetime, painted more than FORTY self-portraits, and this number reflects only those that have SURVIVED. It also doesn't count numerous drawings and etchings in which he used his own likeness to study facial expressions. There is some doubt as to the exact number because there are a few paintings of Rembrandt in which the actual painter is in doubt, and in other cases, paintings in which the painter is not in doubt but the setter IS. (Is it Rembrandt or ISN'T it?) His earliest was done in 1628 when he was a young man of 22. Much of the face is in shadow with the light coming from behind the figure indicating it was probably done as a study of light and color while he was still a student. Another, done a year later, exudes a quiet confidence, depicting, in it's highly polished style, the work and demeanor of a rising young star in the art world of his time.
Rembrandt's self-portraits, taken as a whole, have an eerie quality to them. You can actually see the man age and evolved right before your eyes. His 1862 self-portrait, hanging in the Uffizi in Florence, is rich with impasto but sadly self-effacing. Painted at a low point in his career, only the richness of his colors rescues it from somber flaccidity. His last, painted in 1665 is apparently unfinished, but even at that, appears to be one of his best. It would seem to be a sort of last will and testament--how he wished to be remembered by posterity. In between his first and last are a wildly varying group of visual incantations ranging from the preposterous costumed works to highly dignified renderings consciously painted in the tradition of Titian and Raphael. There are even cases in which he used himself and his wife, Saskia, in disguise as models such as his 1635 painting, "The Prodigal Son." He appears to have used the money he saved in not hiring models to buy the expensive outfits they wear in the painting.