Hi Jim 44.
Do you have more than one email account on the device? If you do, are they from more than one provider? Again, if there is more than one account and provider, is this behavior consistent across accounts or does it apply to just one?
As long as the account(s) are of the IMAP type (which describes most modern email services from larger provers such as iCloud, Google and Yahoo) then there is no danger of losing data so deleting the account and then re-establishing it will be your next best step. Note, the the accounts are with a different service, including accounts tied to a custom domain and Exchange accounts, you'll want to check with the provider before taking this step.
Go to Setting > Passwords and Accounts and tap the individual account and you'll see an option to remove it. Then, reboot and use the steps here to set it up again.
Add an email account to your iPhone, iPad, or iPod touch - Apple Support
Cheers.