Either don’t scan memory, or choose one with a lower sensitivity/thoroughness. From the Memory section of the Scan areas, select one of the other two options.

Personally I can’t see why you bother with a custom scan, the pre-defined Quick and Full Systems scans should be fine.

I schedule a weekly Quick scan, for me that is enough as on-demand scans are for the most part going to be scanning dormant or inert files, any active files are going to be scanned by the file system shield. This depreciates the need for on-demand scans.