If you have a strong opinion about something, and someone asks you about it, you may respond by using the phrase, "don't get me started." The reason that you would say "don't get me started" is because if you started, then the full explanation could take a very long time, because you have many, many reasons.
Frequently, this situation occurs when a person unintentionally introduces a new topic. The listener may have a very strong opinion on that topic, but the original speaker may not have known that this was the case.
Example.
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