Website keeps crashing.... need to find out why!

General information for the business: Local community website
Description of requirements/functionality: Hi

The website of our client's has been crashing frequently since Wednesday evening. The crashes have increased since Thursday and the amount of uptime since then has been very limited.

The site is a WordPress site.

I have logins to the Plesk Control panel where error logs can be inspected.

It may be a simple issue with a WP plugin that's causing too many server requests or may be something deeper. During some uptime yesterday I managed to upgrade the server in the hope that that would improve the situation... it did for a while but not long enough!

I'm looking for a capable individual who can start the process of tests required to find the problem.

If you can indicate how much time you would like initially to try and diagnose the problem that would be helpful.. As you can appreciate it will be difficult to sign off on an open ended number of hours so we just need as much information as possible so we can make the correct next steps.

Cheers
Tim
Specific technologies required: wordpress, mysql, php, server admin
OS requirements: Linux
Extra notes: