for the reflash you can charge and then reflash, but i think that fragos way is right too. follow the wiki and you're surely right.
my n810 was rebooting only while i was moving it, seems like that in yours some service fails and the n810 reboots. i'm not sure but i think i've read something about it, try searching the forum for dsmetools. i'm sorry but i'm in a hurry and i can't help you more than this way.