CD/DVD eject after loading

Try different CDs and DVDs, superdrives that haven't been used for some time may become very picky, but once they start working things may get better. If it spits out disks it means it's unable to read them, usually that's due to a dirty lens. Easiest disks to read are the original music CDs, if it spits out those too, there's not much to do except tearing the superdrive apart and clean manually the inside. If if works with music CDs, next step would be to try using a lens cleaning CD.