This sounds like a heat (Overheating) problem with your Mac. During the import LR uses a bit of resources and make the system run hotter.
There are Mac apps to see what the temps of your system is.
When I restart, all imported images are GONE so I need to start all over and try to remember which images I wanted.
What's up?? I obviously can't continue working this way. Is upgrading to the newest version of LM the answer?
Just to be 100% sure I Understand you, what are you restarting? Lightroom, or your computer?
“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” ― Mahatma Gandhi
The images are probably in the place you selected during import, but not in the catalog.
Lightroom writes to a temporary file during operation, so the information is usually not written in the catalog file until later. Often, this file (called a journal file) can be read at the start of a new session, but in your case this isn't happening. If your photos were copied or moved during import, they'll be at that new location-at least the ones that made it through import before the crash.
Before Importing, try going to Lightroom Preferences in the Lightroom menu on Mac. In Performance, turn off the GPU and see if that helps. If not, turn it back on.
I'm on the 27" 5k myself and not having issues with the more recent versions of Lightroom. (new machine so I've been using recent versions of Lightroom to be clear).