Hot cabriolet stalls in traffic

I’ve got an 87 VW Cabriolet (cute, cute, cute). Runs like a champ, but this weekend it stalled repeatedly while crawling along in stop and go traffic at the beach. Finally, tired of getting ugly looks (and pushing it out of the way), I got out of the traffic and onto a road where I was able to zip along without any problems. There was no indication of overheating (based on the temperature gauge) and the radiator fan was running. I’m guessing something under the hood was too hot, but what? Anyone else have this problem?