DVD and CD-RW problems

A few days ago i started my pc and noticed my DVD and Cd-RW arnt working and dont show in “my computer” Bios dosnt detect them. I started it again next day and they both working fine restarted it and they gone again. It keeps doing it and ive not been doing anything to fix it. When its not workins bios wont detect either drives, the DVD has power and it will open but the CD-RW dosnt seem 2 have power and wont open. But when its working they are good as new? any ideas?