A long-awaited signal of a market bottom appears to have fallen into place during the first week of October, according to Goldman Sachs. Scott Rubner, a managing director at Goldman, said in a trading desk note on Saturday that retail investors are flushing their portfolios and raising cash. "After opening up their Q3 quarterly statements over the weekend, retail has finally blinked. Capitulation is near. This is the last standing asset owner, who has not sold, [and] is moving money right now," the note said. According to Goldman, $89 billion flowed into money market funds last week, the most since April 2020. "This is a massive move. Do not underestimate the significance of this new movement of cash (in addition to selling darling single stocks AAPL and TSLA)," the note said. Until now, retail investors have largely stayed in the stock market despite a volatile year that has dragged the major market averages into bear markets. That has confused many Wall Street strategists and traders who have been looking for signs of a market bottom. Some other signs of capitulation, such as extremely broad selling and indexes falling through long-term moving averages, have been achieved several times this year. To be sure, just because the market has checked off many of the boxes of a capitulation doesn't mean that it will rebound this week. The looming midterm elections could also add yet another layer of uncertainty that weighs on stocks in the weeks ahead, in addition to looming third quarter corporate earnings reports. — CNBC's Michael Bloom contributed to this report.