automatically restart my iphone se(second generation)

Once battery health drops below 80% Apple advises replacing your battery. In my experience once battery health drops below 75% erratic behaviors such as auto restarts, crashes etc. start happening. The fix is replacing the battery.

If you’re in the US please call  1-800-MY-APPLE or outside the US, consult the support articles below. In Canada call 1-800-263-3394

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If your battery health is 73%, the battery is SEVERELY degraded and the only help you need it is to pay Apple to replace the batter in your phone. A severely degraded battery can't be fixed. And even worse things can happen on the phone, like battery swelling destroying your phone.

Schedule an appointment at your Apple Store Genius Bar to have the battery replaced --> iPhone Battery Replacement - Apple Support