There are some interesting stylistic choices made by the artist in this painting. First of all, the colour scheme is particularly bright - a long way from some of his darker, more depressive artworks for which he is most famous. The tall clock to the left helps to frame the scene from that side, covering most of the side of the composition. It also helps us to estimate the height of the Munch who stands alongside it. Both leave a small reflection on the floor, suggesting a smooth wooden floor rather than a carpeted finish.
Behind the doors in the background there is a collection of artworks on the wall and also a greater intensity of light which helps in drawing that detail out. To the right of his room is a long nude figurative painting whilst other elements of interest include the abstract pattern to be found on the bed spread to his left. Most of Munch's interior paintings feature fairly plain rooms, with the artist aiming to remove any necessary items from each composition and focusing most on the balance of light and colour. Compare it to Munch's Night in Saint-Cloud, for example.
Expressionist artists were famously emotional and this inspired most of their work. Introspection was often an element of that and from this would come a whole series of self portraits, in most cases. Munch was no different in that regard, producing many different self portraits during his career, in a variety of styles and mediums, including many drawings too. In some cases it was not entirely clear if it was a self portrait or not, but there is certainly no lack of clarity within this particular painting. The true masters of self portraits would probably have to be Frida Kahlo and Vincent van Gogh.