What programs have you installed recently? How much RAM is installed? 16GB has been known to cause instability in some models.
And also, did any of your recently installed apps not originate from the official Map App Store?
I'm not saying that downloading apps from places other than the Mac App Store is necessarily risky; there are tons of innocuous sites you can download and install apps from.
Where do you allow app downloads from? The safer options are, as you would expect, "Mac App Store" and "Mac App Store and identified developers"...
I obviously can't say that you having used one of the less safe options is causing your freezes (notice I have the last safe option selected and I've had no issues), and
@rambo47 's information is just as likely to be causing these freeze-ups on your system, but just wanted to share this info with you...