What Topics Should I Write About?

I suggest you start with exploring your motivation for keeping a journal.

I was going to write about why I wanted to start it but I would like questions and topics for after that ordeal.

But the examination of your motives should yield something about your concept of "self", and self can be a significant topic for discussion. Some philosophers, for example, think it is a socially acquired by product of language. Others argue that "self-awareness" may or may not distinguish humans from animals. It may even be the case that such explorations lead you to abandon "journal writing" altogether !

Is this journal you're writing going to be private or published somewhere?

Please abandon "journal writing", but not journal writing.

the lack of topics in philosophy

What is it that you don't understand about inactive threads? This thread was last replied to 18 months ago. The OP and many contributors are not active any longer on the forum.

and yet you still replied