Hello, networkmom, & welcome. Gosh there’s a lot you don’t tell us, ie, whether your host is shared, VPS, or dedicated; what your version of PHP is; & no site url for us to have a look.
Some hosting providers allow upgrading of the PHP version in their control panel. If you have old plugins &/or themes on your site, however, they may not function after the upgrade. It’s always best to go through your site from time to time, & if a plugin or theme hasn’t been updated in a year or more, to try to find more current software that will meet your needs. You might also try contacting your host & see if perchance they can assist. Disabling all plugins to see if the problem goes away & then re-enabling them 1 by 1 till the problem reappears will let you know the culprit plugin. Also, changing to a default theme (the theme name will always begin w/twenty) as a temporary measure to see if the problem goes away. If so, then pretty clearly the theme is at fault.
Hopefully you’ll find some of this helpful. Please let us know.