Impala cut off but dash/headlights/radio still on

I was driving fine, then I stopped at a red light. My heat has always had problems, some
guy told me my ac/heat fans were getting stuck, or something, when I moved the switches
to switch from ac to heat... But anyways, I was sitting at the light, I decided to flick the heat
to ac then back to heat to get some heat flow(which has worked previously), but this time
my battery shut off--dash/headlights/radio were still on though-- but I couldn't drive. So I
restarted the car, without messing with the heat switch(which was working normally now)
and from there things were normal, besides I had a feeling my car was struggling to
accelerate, not extremely noticeable, but I could sense it a little... Please help :(