Hi,
As you can see by my feedback I have completed lots of windows admin work for various clients on here, I’m also UK based which I see you are so am available to chat on the phone if needs be! My gut feeling is this actually isn’t a windows issue however, off the back of what you’ve put it undoubtedly points to the SQL instance getting overloaded, which is why you notice the extra php processes as they are sat there waiting for the SQL to reply (and also is why restarting it alleviates the problem temporarily)
A little about me:
I have over 15 years system administration experience with a number of distributions of linux / unix and windows server, working for a large number of blue chip companies here in the UK.
Skill-List (Including but not limited to):
Windows 2000-2016 Server
Exchange 2003-2016, Office365
Linux / Unix Administration
SAN Storage (NetApp, EMC Clariion, HP MSA/EVA/Lefthand)
Server Virtualization (Vmware ESX, XenServer, Openstack)
Desktop Virtualization (Vmware View, Xen Desktop)
Application Virtualization (Thinapp, Xenapp)
Networking (Cisco, Juniper, HP, Extreme, Ubiquiti)
Firewall / IDS (Cisco, Fortigate, Juniper)
Backup (CA Arcserve, HP Data protector, R1Soft, Veeam)
Server administration (MsSQL, MySQL, Oracle (inc forms & reports), InnoDB, IIS, Apache, SCCM, WSUS)
VoIP Solutions (Nortel, Avaya, Shoretel, Asterisk, FreePBX)
Penetration Testing / Server Security/Hardening
WHMCS, DirectAdmin, cPanel, Webmin
AWS, Azure Config/Management
Lawrence