Other than it trying to eject at startup, does the drive otherwise work normally? That is to say, does it go into "eject mode" at startup and keeps trying to eject forever, or does it go into "eject mode" at startup and then stops after a little while and then you can insert a disc and everything works fine afterwards?
First thing to try is cleaning around the eject button. It's possible something sticky got in there and the button is being held down . Unplug the device, get a toothbrush and a bit of isoprypyl alcohol (91% or better), dip the brush in the alcohol and scrub around between the button and the case. Wipe it down, allow it time to dry, then reconnect and give it a go.