Were you driving in wet weather by any chance?
If the then maybe your distributor cap/plug wires need replacing.

Happened to me before. I stuck a trouble light (100 watt bulb in a metal cage) under the hood for 5 or 10 minutes and the heat from that dried her out pretty good. She worked fine after that and the next day I sprayed her wires with a clearcoat type of wire dressing. Lasted for about 2 years like that. The next time I bought a new distributor cap and upon closer inspection the old one actually had a nice crack in it.... oops!