I asked about rebooting because, IIRC, that will clear your RAM. At least that was true in Windows 7. I haven't dared to go to Windows 10 (yet). Too many unresolved issues.

I hesitate to recommend third party apps but Wise has a great system toolbox that I use successfully. It has a RAM Optimization tool that maximizes RAM.

The Pro version was available free at www.majorgeeks.com I think it's now $29, not certain.

Donny