Begin this pattern using your second (middle) finger. In the fifth position, you will need to shift your hand position up a fret on the second string. Stay in this new position for the notes on the second and first strings.
When descending the scale, stay in this new position for the first and second strings. When playing your first note on the third string, use your fourth (pinky) finger, which should naturally shift your hand back into the initial hand position.