Who chooses?

What makes that I choose this and not that? Is it I who makes the choices or is there something in me that makes the choices for me? For example, a Cartesian homunculus? If it is I who makes the choices, who or what is this I? Alternatively, if there is a kind of homunculus in me that makes the choices for me, can I say then that I do not like the choice and refuse to execute it? Or am I forced in some way to execute it? In the first case there can be no homunculus that chooses for me, for in the end it is I who makes the choices. In the second case, I seem to be determined to follow the choices laid upon me, but what is then the difference between me and the homunculus? It is weird that there would be something in me that decides in my place, but sometimes I have the feeling that I do things that I do not want to do but that I am forced to do for an unclear reason like a puppet on a string.