The do statement is improperly indented. Some white space after the while statement would be useful. The { on the next line is unnecessary, as is the matching } later.
for(pos = 0; pos < 180; pos += 1) // goes from 0 degrees to 180 degrees
{ // in steps of 1 degree
myservo3.write(pos); // tell servo to go to position in variable 'pos'
delay(10); // waits 15ms for the servo to reach the position
}
for(pos = 180; pos>=1; pos-=1) // goes from 180 degrees to 0 degrees
{
myservo3.write(pos); // tell servo to go to position in variable 'pos'
delay(10); // waits 15ms for the servo to reach the position
}
Why bother waving the servo around? It isn't accomplishing anything.