Do you sleep with your phone by your bed or in another room?
The best practice is to sleep with it in another room, but if you need to use it for an alarm, turn it on airplane mode right before you drift off to sleep.
Your alarm will still work, but your phone will stop emitting radio waves and wifi signals. Having this long break from everything your phone emits every single night will add up to a large sum of hours these signals are not bombarding you. You’ll even sleep more soundly!