This is not an issue that I can state many are or have experienced. That would mean that there is some issue of the software running on your individual device. That's easy enough to resolve though, luckily. It's nothing like the days of Windows 95!
First, I would stop listening to those suggesting that you hold your lock and home buttons to restart your phone anytime something weird happens. That's the same logic of pulling the power plug from the wall anytime you want to reboot your desktop computer. It's not good for the phone or its software.
Second, I would start by backing up your phone through iCloud or iTunes (I preference iCloud). How to back up your devices using iCloud or iTunes - Apple Support
Third, restore your phone to factory settings. Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings - Apple Support
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Restore your backup onto your phone and after the phone has had a few hours to properly recatalog its search library, see if your issue is not resolved.
In the worst case scenario, there is some data that has gone bad in your software which can be restored through your backup, and the issue will continue.
If this ends up being the case, follow the article on restoring your phone to factory settings again, and then proceed to setup your phone as New. Avoid restoring from any backups when offered, and proceed to sign into your email accounts through Settings>Mail, Contacts, Calendar and Apple ID(s).
You can re-download or sync your purchase history from there, same as you always have.
One more article to share: Import photos and videos from your iPhone, iPad, or iPod touch - Apple Support
Just in case you have some photos or videos which you want to create a separate redundancy of from your backup files.
Contact AppleCare Support at 1(800) 275-2273 if you need any further assistance or guidance. Their phone support has been a free service for nearly a year now.
