Translation:I want to discuss this issue today.
"Today I want to discuss it" is indeed a strange construction, but for a specific reason: you cannot stress "it" in English. "Today I want to discuss that" or "Today I want to discuss this issue" are OK though: you would say that if you wanted to stress "that"/"this issue": these sentences tell you what we are discussing today, not when we are discussing something. But in this case the Russian word order would also be different: "Сегодня я хочу обсудить этот вопрос".
If I understand this concept correctly, "Я хочу обсудить этот вопрос сегодня," means that we're going to get to the bottom of this today. We will have discussed it and resolved it by bedtime. Whereas, "Я хочу обсуждать этот вопрос сегодня," is more like I'm working on a thesis and I need to do some conversing on this topic, but I'm not necessarly expecting to finish anytime soon. Is this correct?