How can I improve this circuit to drive a servo with a 555 timer?
Try adding a second LM7805 and use it just for the servo power.

Use a &quot;star&quot; ground connection.

100nF ceramic capacitor bypass near the 555 in addition to the 100uF

In conjunction with the first point, bypass pin 5 on the 555 to
ground with a 10nF ceramic capacitor.