It is normal and accepted to answer one's own questions. Other answers have pointed out that quality still matter, but I think more can be said about the topic of quality.
As far as I see it the best question for a self-answer is a question that requires some substantial research or substantial experience with the technology which is the subject of the question. Since these questions require substance it is unlikely that one would be able to knock them out in quick succession.
At the opposite end of the spectrum, the self-answers that I see most often are those that amount to typos, or that are due not reading the manual. It is extremely easy to post these in quick succession. They are not very valuable.
In a few extreme cases, I've seen some users submit a bunch of "read the manual" type of problems, with self-answers. Reading these Q&A felt like reading a manual for the technology. They did not elucidate an obscure point, or solve a problem that required bringing together multiple parts of the documentation. In effect, it felt like these folks had decided that they would seed SO with questions and answers that were trivially answerable from looking at the documentation and reap the reputation. I flagged them and their posts disappeared.
Consequently, in my view, the more frequently one posts answers to their own questions, the less likely that these questions are high quality questions. Is it a hard and fast rule? No. Someone could work on a bunch of really hard problems, format these in a Q&A format and post them to an SE site in close succession. But it is something to keep in mind if one finds oneself answering one's own question frequently.