This is a new mechanism to augment the low quality question ban system.
Instead of outright banning users it will rate limit them. I believe the limit may be variable but I have seen a potential of 1 question per week.
The upshot should be that it is harder to get banned by asking questions that are poorly received, the downside is that you are instead rate limited until you gain enough high quality posts.
This link Why won't the system allow me to ask questions for several days? suggests that the system was only live to SO, but is is possible it has been enabled network wide.
How is the length of time that I'm limited actually calculated?
It's based on your average question score, how long you tend to wait between asking questions, how well you participate in other ways on the site, and how often you tend to revisit and improve your posts, even the positively scored ones. We don't provide the actual formula and details, but only because we want folks to focus on what the system is trying to tell them, rather than trying to find ways around it.
Rate limits vary from 1 to 7 days.