Constant rebooting is not normal and should not be acccepted. I had a similar problem with my X from release day. It was good for almost 2 weeks and then started locking and random reboots. Could be an app you have installed. I did a Factory Reset, and didn't install any apps at all and it was still locking and rebooting within an hour. At that point, it was clear it wans't anything I added.
Best advice is:
1) if you noticed this specifially start right after you installed an app, uninstall that app and see what happends.
2) If it continues, do a Factory Reset, and let it run for a day without installing any additional apps. If it is still rebooting, take it back to the store and have it exchanged.
3) If after Factory Reset issue is solved, add apps back slowly and if it happpens again, note the last app you added and remove and see what happens.
Rebooting on its own is NOT NORMAL and 2.2 likely will have little impact.