In order to troubleshoot such issues you have to check the internet connectivity to your server. Here are some tips:
- Run ping and traceroute checks. Compare the results with other sites. Usually results with less than 200 ms are fine and do not indicate problems;
- Try working in your control panel (cPanel, Plesk, etc.);
- See how fast mails download.
Most shared hosting servers are situated in the USA which is a priority destination for all Internet service providers. You can find where your site is hosted from here or other online tool. Connectivity affects greatly your site when on it you have:
- Flash animations;
- Big graphics;
- Huge file downloads;
- Video/Audio files.