You don't have an electrolytic across the supply to the servo - try a 100uF across the 555 supply pins. Also bear in mind you're feeding the motor from the output of the 5V regulator, this may cause it to current limit? - and assuming the 9V supply is a PP3 type, this probably doesn't have enough power to feed a motor anyway.
I would suggest fitting an electrolytic across the 555 supply (always essential), throw the regulator and 9v battery away, and power it from 4 AA alkalines in series (6v).
I would suggest fitting an electrolytic across the 555 supply (always essential), throw the regulator and 9v battery away, and power it from 4 AA alkalines in series (6v).