Yes, it's a common problem on shared hosting. To control and stabilise the traffic to an individual website, most hosting providers set the max cap for memory utilisation. The outcome of which, each website can share feasible memory.
As your website is WordPress CMS based, you can follow below steps.
- Open cPanel > Filemanager or FileZilla / FTP Client
- Navigate to public_html directory
- Edit wp-config.php
- Insert the following line anywhere (must on new line)
Done..! Now refresh your website.