Yes...happened to me once, am with my sister, coming from a relatives' party in manila, we're already at the stretch of aguinaldo hi-way, my sister was talking endlessly that time, pero nakatulog pa den ako, split second lang, wala naman masyadong sasakyan, pero kinda scary pa den, i really couldnt figure out how that happened...after nun naging sobrang sobrang ingat ko na...siguro kasi past my bedtime na den and na-imagine ko na yun bed ko......tama si GH, dapat kung medyo sleepy ka or feel mo hindi ka pa fit to drive, magpahinga muna few minutes...