Have you checked to see if any OBD codes were set? Can you correlate these problems to wet conditions (rain/snow)? Being so erratic, it sounds electrical. But the problem is there are a bunch of usual suspects - coil pack, crank/cam position sensor, exposed/lose/cracked wire(s), TPS. But there are other possibilities as well, and hanging parts starts to get expensive fast. Plus, it's also possible the problem is fuel-related (pump, filter, injector). Best to diagnose, but that requires some know-how, and a probably a good manual. If you haven't done so already, check to see if a code was set, which might point to the exact problem. The erratic ones can be a real PITA