My iPhone 18 Pro Max has restarted unexpectedly twice—once yesterday and again today. There's no pending software update, and the phone has plenty of available storage. I later realized both restarts happened when I double-clicked the side button to confirm a purchase. Is this a known issue, or is there something I should check, such as the software build number?
2 Answers
Check the phone’s software build number and confirm that storage isn’t nearly full, although you’ve already ruled out the most obvious storage issue. The build number is usually available under Settings > General > About, so you don’t need the original box. If the unexpected restarts continue, save any diagnostic information and contact the device manufacturer’s support team for a hardware or system check.
That isn’t considered normal, so the timing is important. Pay attention to whether the restart happens only when using the side-button purchase confirmation, Face ID, or a particular app. Since both incidents followed a purchase attempt, it could be related to the payment or authentication process rather than a general hardware problem.

Both times were right after I double-clicked the side button to confirm a purchase. I’ll keep track of whether it happens with one specific app or payment method.