Solidworks 2018 performance

Hi

I've just started using 2018 on Win 10.  Was using 2012 on Win 7 before.

Whenever I do something minor (for example, I've just deleted an assembly-level sketch that had nothing referenced to it) SW churns away for 2-3 minutes.

This never happened on 2012.

I've got a decent PC - Core i7 processor, 32GB RAM, 4 GB Nvidia GPU...

Any ideas of stuff to check?

Thanks a lot

SolidworksAssemblies