I'm writing an academic paper on ethics in robotics. I have a previous paper that I wrote and would like to use material from it. If I use the material from this paper, that I wrote, do I need to cite myself as a source in the new paper or am I free to use my own material again without citation? These are my thoughts and ideas, not others (I realize that I would need to source others work again if I used it again).
You cite a source because it gives additional information that a curious reader may want to follow up on.
So: If your prior paper gives additional information (data, methods, background, conclusions, further citations, etc.) that is not in your current paper, but which may be of interest to readers, cite it.
By the way, you're not citing yourself; you're citing your paper.