I have an iPhone SE. Periodically throughout the day, the phone shuts down and restarts. This will happen whether I'm using it or not, such as in the middle of a phone call. I thought it was a problem with my old phone, an iPhone 5s. But it is still happening with the new phone.
Oh no! Having your device working correctly at all times is vital, and it is definitely unusual that this is happening with two device Divagnat2. When did you realize this started happening? Have you been having this issue since you bought the new phone?