KOBO insisting on resetting from new

[kangxi]

My Kobo is acting up. First it changed how the search function worked. (it used to search automatically within the book I was reading, then lately changed to choosing the current book via a series of drop down menus). Then it couldn't find anything I searched for. Last night it wouldn't open any book at all claiming DRM problems. Finally it shut right down and on trying to switch on it went into what looks like a boot sequence and will only open as if totally new, demanding I first choose a language then set up my wifi. During all of this my wifi was switched off so if it got any outside upgrade then I don't know how, and I assume it's all an internal problem. I cant remember which model it is - it says Rakuten Kobo on the back, the whole thing is 160 x 110 mm and the screen is 120 x 90 mm.