Before starting and after ending, the Shemone Esrei, we take three steps back and then
do three steps forward.
The original Takanah was, at starting the Sh.E, only to step forward (not backward).
At the end of the Sh.E. only to step backward (not forward)
The Darkei Moshe( O.Ch. 95) quotes the Rokeach “ It says three times Vayigash by Tefillah,
therefore you should step forward three steps.” (before starting Sh.E.) (no mention of stepping back)
The Mishna Verura (95 sk 3) quotes the Elya Raba that it is not necessary to step back
before stepping forward. However the M.V. adds in the name of the Magen Giborim , the Minhag Haolom*1 is to step back before stepping forward.*2
The M.V. (123 sk 8) writes,(at end of Sh.E. ) it not necessary to step forward. Only according to R. Manoach in Bais Yosef *3 who holds you need six steps, you do three backward
and three forward.*4
1* It is very likely that it is done for practical reasons, so to end up in your original spot (place).
2* The Kitzur S.A. writes to step back before saying Goal Yisroel and step forward after
saying Goal Yisroel.The reason probably is, stepping back is not part of Tefilah –Hefsek
stepping forward is part of Tefilah hence no Hefsek.
3* In Shulchan Aruch there is no mention of the shitas R.Manoach (only 3 steps)
4* see Bais Yosef numerous reasons for stepping backwards none apply for
stepping forward. (except R. Manoach- 6 steps)