This is in the top tier of the LAMEST excuses I ever get for why people are sitting there like bumps on a log. As far as phrases that make me want to rake out my own eyeballs with a fork, it is second in severity only to the question "Is it safe?"
By the very virtue of your being able to read this post, you are aware of this thing called the internet. You can pull the Library of Congress out of thin air at a coffee shop on your phone. You are most likely at least vaguely aware of a small company called Google that assists people in locating specific information.
Anyone can become an absolute expert on anything in record time. Never in the history of history has information been so available to so many. If you persistently hide behind the excuse "I don't know where to start," I see a couple of possibilities:
1 - You are an incompetent and babbling fool that should not be allowed in public without adult supervision.
2 - You need to rephrase the statement to read "I don't really care enough about (INSERT NOBLE CAUSE HERE) to actually do anything about it but if I express sympathy and dismay at my inability/lack of desire to exert effort to be involved in making a positive impact, then I hope to generate sympathy from the listener and then I can fade into the background with a feeling that may almost be the same as actually doing something. If I'm lucky, the listener will also say well you can just do (INSERT MENIAL TASK RESERVED FOR UBER SLACKERS BY NGOs HERE) and I can say I contributed and I never have to look back and/or do anything about it again as I pat myself on the back over and over again." (yes I know everything above is a grammar catastrophe but it is a thought catastrophe that leads to it so I'm trying to be consistent).
The reason the word is called "START" is because that is the BEGINNING of your journey. If you think you can jump into the complex issues of the world today and be instantly ready to solve the problems, without going through a severe and steep learning curve, you will fail 100% of the time. You cannot get to the point of maximum effectiveness, however, until and unless you are willing to "get there" honestly.
Pick your Noble Cause. Not all of them....ONE of them...and go full throttle into attack mode. Learn about it. Find people doing something about it. Discern which of the people doing something about it suck and which ones are awesome. Partner with the ones that are awesome and at some point it may be necessary for you to peel off and do your own awesome thing.
Whatever you do, just don't let me hear you making lame excuses. I'd rather you just sit there quietly being that bump on a log than have to listen to it.