So my Sentra justs dies.(for a moment)

I have a dilemma with my 2001 Nissan Sentra. It has 35,520 miles on it.

Recently I was traveling in very hot weather with the A/C going full blast. My first inkling of trouble was when I went to get on the highway, I had had trouble getting up to speed, The Tachometer went to 4000 plus. I had to punch it a few times to get the RPM relative to the speed to be where it should be(this never happened before). then about 20 miles later, going uphill the car just dies on me. I would not re-start. I would turn over but then I would promptly die. I had to waited about 20 minutes and it finally restarted and ran normally. When I started it. The temp gauge was normal(I did not notice the temperature before it died.)

Help! Who can tell me anything?