If you keep asking the "why"-question you should be able to trace back your reason for doing anything to its foundation. So what could this look like?
Well first I would have to know what exactly I even.. well what do I even know?
In 1637 René Descartes recognized "cogito, ergo sum", usually translated to "I think, therefore I am". This statement encapsulates everything I as a conscious entity can know.
Now, there is no way to know if there is any sort of objective meaning or truth to life, however there is a sense of "living" my person can experience. Disconnected from any meaning this state seems naturally good to me.
Therefore:
I exist
I experience a spectrum of a sense of living
I want to increase my sense of living
Outside of my thoughts there seems to exist a physical plane on which I can act filled with other entities. These observations can however never be verified so I am once again left with no choice but to accept my senses to be true as they are all I have.
These other entities seem to act similar to me from which can be concluded that they probably also experience a sense of living which they strive to increase.
Therefore:
Other conscious entities exist
Other conscious entities experience a spectrum of a sense of living
Other conscious entities want to increase their sense of living