Initiative is deciding the problem has waited long enough for somebody else.

Waiting for someone else to handle a problem is usually reasonable and occasionally permanent, because everyone is waiting for the same reason. Initiative is not heroism, it is simply the moment you decide the wait has gone on long enough and the cost of continuing exceeds the cost of acting.

Think of something you have noticed for months that nobody has fixed. Ask what would happen if you did the first part of it yourself. Often the reason it persists is that it belongs to no one.