SQL-Server-First-Responder-Kit VS sp_whoisactive

I would also check that the server is configured according to best practices - DBA Dash can also help with that. I would also recommend running sp_Blitz. In terms of memory configuration, you should set the max server memory to an appropriate value.

Either sp_WhoIsActive, or you can look into First Responder Kit - https://github.com/BrentOzarULTD/SQL-Server-First-Responder-Kit/tree/main - specifically sp_BlitzCache stored procedure, which, by default, will list out the most CPU expensive query in SQL Server plan cache. This should help you identify the "problematic" query.

Someone mentioned Blitz scripts - these are a series of free, open source stored procedures that are simple to instal and run on your SQL instances. You can find them here (https://github.com/BrentOzarULTD/SQL-Server-First-Responder-Kit) and at his website (https://www.brentozar.com/blitz). To be honest, I admire the guy and how he presents help and techniques on how to trouble shoot your SQL instance - so I would start with the sp_blitz sp, run it, follow some of the links provided in the results and start learning a few things from that.

then download this and install it on all of your servers (i recommend having your own DBA databases on each server that you stick your tools in): https://github.com/BrentOzarULTD/SQL-Server-First-Responder-Kit

You could use sp_ineachdb(which just uses a cursor under the hood)

SQL Server First Responder Kit, Ozar et al. The First Responder Kit is a set of stored procedures for "first responder" consultants who want to troubleshoot SQL Server problems. Coupled with the various resources at brentozar.com, the kit gives a great set of tools for performance investigations to gain a strong foothold and then make immediate progress on key issues and low-hanging fruit. The resources at the site develop a strong understanding of SQL Server internals for iterative refinement.