Hi Rhonda,
Have you tried doing a restore using what's called DFU or Device Firmware Upgrade mode? It's the most complete wipe and restore option possible on an iPhone and can sometimes help when nothing else has. If you've only done the standard iTunes update and restore options, then this will definitely be worth a try. This page has a fairly complete description of DFU mode on your phone.
How to Get into DFU Mode on iPhone 8/8 Plus/X - EaseUS
The relevant part you need to know is this.
1. Connect your iPhone 8/8 Plus/X to a computer using a USB cable.
2. Quick-press the Volume Up button
3. Quick-press the Volume Down button
4. Hold down the Side button until the screen goes black, then hold down both the Side button and Volume Down button.
5. After 5 seconds, release the Side button while continuing to hold down the Volume Down button.
6. If the Apple logo appears, the Side button was held down for too long.
7. Nothing will be displayed on the screen when the device is in DFU mode.If open, iTunes will alert you that a device was detected in recovery mode.
Of course, have a good backup because this will wipe everything on your phone.
Once you get to this point, if the DFU recovery doesn't help then you may well be looking at a hardware problem. You could try removing the SIM card and see if that makes any difference, but otherwise you might have to consider taking it to a repair shop to have them see if they can figure out what's wrong with it.