iPhone SE (2020) randomly restarting on its own?

Go to Settings > Battery > Battery Health and Charging, what is your battery health at? You should have replaced the battery in your iPhone at least once by now, and frequent shutdowns can indicate a significantly reduced capacity battery. If the battery health is below 80%, you should get a battery replacement.

Please also try a Forced Restart. Perform this operation quickly, and ignore the slider that appears.

• Press and quickly release the volume up button.
• Press and quickly release the volume down button.
• Press and hold the side button until you see the Apple logo 

Lastly, if the Forced Restart doesn’t work and whether you need a battery replacement or not, I would suggest you make a reservation at the Genius Bar or an Authorized Service Provider for service.

Genius Bar Reservation and Apple Support Options - Apple

If you find an authorized Apple service shop in your area, it would be a good idea to call them to make sure that they have the battery you need in stock.....before....you take the phone in.

Otherwise, your phone will sit in the shop a few days waiting for parts.

In most cases, you should plan to drop the phone off and pick it up a few hours later, since the technician will not stop what they are doing at the time to replace the battery in your phone. Sometimes....if the shop is really slow at the time.....you might be able to wait the 20-30 minutes while the battery is replaced.

You are very welcome! The link I will provide below has a list of all the Apple Stores and Apple Authorized Service Providers you can view by entering your city or zip code. Open it then tap Service and Support. Be sure to only visit one of them and not a non-Apple Authorized Service Providers as they do not have genuine Apple parts and the proper training to service Apple products. Furthermore if you were to do so, they would void any Warranty or AppleCare+, and Apple won’t ever touch the iPhone again. Glad to have helped!

Find Locations