Yeah, I think you’ll need to send it into service. Hard freezes can indicate a variety of problems…CPU, memory, supporting chipsets, etc. If it was freezes when there was no physical movement then it might be driver related…but that doesn’t seem to be the case.
If you can be without your system for a bit, I’d have Sony look at it. Just make sure you can duplicate the problem multiple times before sending it in and give them a note (i’d tape it to the system) to tell them exactly what to do for it to freeze.