The Shulchan Aruch (103:2) states:
בקש לצאת ממנו רוח מלמטה ונצטער הרבה ואינו יכול להעמיד עצמו הולך אחוריו ארבע אמות ומוציא הרוח וממתין עד שיכלה הריח...וחוזר למקומו וחוזר למקום שפסק
If a person has to pass gas and he is unable to hold it in, he should walk backward four amot, release the gas and wait until the smell subsides...and he should then return to his place and to the point in the tefillah where he left off
From this it seems that one would not be required to take three steps when one pauses and subsequently resumes his shmoneh esrai.
As well, the Shulchan Aruch later states (123) the halacha that one should take these three steps at the end of the shmoneh esrai in "דינים הכריעות בסיום שמונה עשרה ברכות - The Laws of the Bows at the Conclusion of Shmoneh Esrai" which seems to indicate that these steps would only be required at the conclusion of shmoneh esrai and not merely for a pause. This also seems to be the intention of the source for this rule (Yoma 53a) which draws the rule from a servant taking leave of his master. Again, this would only apply if one was taking leave and not merely pausing.
Regarding the three steps forward (at the commencement or re-commencement of shmoneh esrai) these steps do not appear in the Talmud (as far as I have found) like their end of Amidah counterparts. They make their first appearance in the Halachic works of Rabbi Moshe Isserlis (the REMA), both in the Darkei Moshe and his gloss on the Shulchan Aruch in Siman 95. He brings this as a “yesh omrim” from the Rokeach and only mentions the three steps forward. He explains that the reason for the three steps forward is because there are three places in the Tanach which the word “vayigash – to approach” is used regarding prayer, Avraham, Yehuda and Eliyahu.
Restarting shmoneh esrai would, seemingly, not be considered “vayigash – to approach” being that the "approach" already took place and being that these steps do not have their roots in the Talmud it seems that they would be unnecessary in this situation.