8 month old sleeping face down?

A little back context here. My baby is 8 months old and sleeps in her crib with no toys or blankets. I use cotton sheets on her bed as well. She can rollover front to back and back to front as well as i believe she may start crawling soon. My issue is every 15 minutes while shes asleep she rolls over and sleeps FACE DOWN on her matress. Her head is not to the side but her nose and mouth are flat on the matress. Is this even safe? I cannot go to sleep knowing shes like this. Everytime i flip her she wakes up and its another hour to put her backbdown. I feel like its interrupting both of our sleep. Is it safe for her to sleep face down like that? What can i do to stop it?