"You need to restart your computer" freeze while waking up
No, this is not a common issue and should not occur under normal circumstances. It's an indication that something unexpected (and unrecoverable) happened. That screen is the final net for catching a problem before your computer is completely locked.
If you just got new RAM, I'd try removing it an using the computer for a few days. If the problem persists, there might be a hardware problem and since the computer is new, you can take it to an App Store.
If you have "external" peripherals (drives, Audio interfaces, etc.) try working without them for a while. 


Last but not least, act now that the box is new, don't let it "wait" because it didn't happen again in two weeks. If the above happened more than once in a short time frame on a new machine, there's something wrong. That's been my experience.