Hi bella-tart123,
Thank you for using the Apple Support Communities. From your post, it looks like you see a gray screen on your iPhone, and you're unable to force-restart your device. We'll be happy to help!
Do you see anything else on screen, like an Apple logo?
Also, does this happen only when you receive a call? Does the issue eventually seem to clear up and return you to your Home screen?
Are you using these exact steps to force-restart? If your iPhone, iPad, or iPod touch won't turn on or is frozen
If your screen is black or frozen, you might need to force restart your device. A force restart won't erase the content on your device. You can force restart your device even if the screen is black or the buttons aren't responding. Follow these steps:
- iPhone 8 or later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Side button until you see the Apple logo."
Depending on how that goes, there may be a few other steps to try, but they'll depend on a few specifics.
Which iOS version are you using?
Have you backed up recently?
Let us know here and the community may be able to help out with that information.
Kind regards.