This usually points to the some other background process kicking in and stealing system resources, such as:
- Virus Checker (including Windows Defender)
- Windows Indexing Service
- OneDrive
- Windows Update (or any other update like Google, Apple etc - Adobe & Java normally only do their checks on startup)
I either disable or set these to manual.
Also make sure you've not got any browsers open. Google ads on websites are a real PITA with javascript running in the background.
M.