I know 5 people who got shift, 3d evos etc and its happening on all of them. Its seems to me like a big issue and no way user error.
is your device actually restarting or is it simply the Sense launcher. I remember when ever I used something that was pretty intensive memory wise (or at least I thought it to be) when going back to the home screen you would get the htc sense screen (just like a reboot) but it was very quick because it was just the launcher and not the actual phone restarting.
If that's the case, and this is just my opinion, it sounds like your phone is running low on memory and putting the launcher at a lower priority over other things (it needs to kill something to free up memory).
Even now, after I rooted my phone and running launcher pro, I still have that same issue where the launcher restarts although if you keep your launcher cleaned up I find that it restarts more quickly and less often.
I would try a different launcher if this is the case or maybe remove some of the things on your home screen. I'd imagine that if you have a lot of widgets and so on running on your home screen it is going to use a lot more memory.