Unity 5.3.5f1 is unusably laggy

I installed unity 5.3.5f1 on my machine yesterday and trying to work with it has been basically impossible. It will randomly lock up for 5-10 seconds at a time when I'm trying to work with an almost empty project (scrolling, selecting things in menus, maximizing the window after minimizing it to ask google why it's going so slowly).

I've found several posts online going back several years that seem to have similar problems. The fixes suggested in those posts haven't worked for me. They include adding switches to force rendering modes (opengl, directx9, directx11 single threaded). They've mentioned nvidia control panel settings, though I haven't seen any options that match up with what my control panel shows.

My laptop from 2011 ran unity fine when I was working with it last year. My current machine has these specs (and seems to work fine running everything else, including Elite Dangerous and Project Cars)

• Windows 7 Pro (64 bit)

• Intel Core I5-2500

• Nvidia GTX 1070

• 16 GB ram

• OS and unity both on SSDs (separate drives if that could maybe matter?)

Has anyone else had these problems with the latest version? Any suggestions on what to try?