Bitcoin began the week on fragile footing, hovering near $108,600 after briefly bouncing from a weekend low of $107,500. The world’s largest cryptocurrency has shed nearly 10% since mid-August, when it reached a high of $124,500. September is adding to investor unease—historically, the month has averaged nearly a 4% decline for Bitcoin since 2013, earning it the nickname “Rektember.” ETF flows reflect the shifting sentiment. U.S. spot Bitcoin exchange-traded funds logged $126 million in outflows on August 29, ending a six-week streak of steady inflows. For the month, Bitcoin products lost $751 million, a sharp reversal from the $6 billion inflows seen in July. Analysts warn that failing to hold support between $112,000 and $115,000 could open the door to a deeper slide toward $103,000. Still, underlying conviction remains. Bitcoin’s “realized capitalization”—a measure of coins priced at their last transaction value—has climbed to a record $1.05 trillion, signaling that long-term holder...