Jim Cramer, host of CNBC's show, advised investors to be cautious when German sandal maker Birkenstock goes public this week. He suggested that investors should avoid the "initial feeding frenzy" and wait for the stock to cool down before considering buying shares. Birkenstock is expected to have a $10 billion valuation and is seeking to price its shares at the top of its $44 to $49 range. Cramer expressed concerns about the stock being too expensive right after the IPO and questioned whether Birkenstock's popularity is a fad or has lasting power. He also noted that a significant portion of the company's shares are already spoken for by big-ticket investors. Cramer advised against buying the stock in the open market and suggested waiting for a better opportunity.