Intermittent noise and tracks drop out

I’m running Cubase Elements 11.0.10 on a Windows 10 machine. Lately I’ve been experiencing short periods (1 to 2 seconds) of noise. (Happens both while transport is playing and when its not.)
I’ve restarted the PC, stopped Norton 360, and opened different songs. The noise still occurs randomly.
It’s relatively quiet, and only happens while Cubase projects are opened.
I also am experiencing tracks dropping out during playback. (The dropouts do not occur during Exporting mixdowns.) I’ll go back and play the dropout section and it plays fine. The problem isn’t in the midi.
The songs average about 10 or so tracks.

Sound like a demo trial plugin…

That would be an excellent choice but I’m not running any demo’s. In fact, I’ve gotten rid of a couple or rarely used VST’s in an attempt to fix the problem, and to do some house cleaning.