ill b the bear who suggests a big leftfielder... this happened 2 me 2 recently - endless onoffonoff bootloop turned out 2b a corrupt bios* but the mobo couldn't detect it 4 sum reason thankfully sed mobo had a backup bios so I shorted v+ and gnd on m_bios chip with my multimetre & pwrd up no pwr 2 the chip jogged it into recovery mode & it tried 2 reflash m_bios from b_bios (but failed obv) so I did it agan & just b4 the 'dual bios recovery" appered I pulled my multimetre of the pins 1 self reflash l8r & the mobo has been workin perfectly since * was nice of my gf to mentin DAYS l8r "oh it flashed up some bios error"