Also I should have mentioned that I'm using a bluetooth mouse and keyboard. The lag happens with both a keyboard click (such as the delete key) and mouse actions equally. Doesn't seem to be related to those since those 2 bluetooth items work just fine in other programs.
Ok for some unknown reason - right after I posted this question, Illustrator stopped lagging!! I thought surely the problem would start back up but it's been 24 hrs and it hasn't happened again. Fingers crossed.