Resistors build up heat and often they are nothing more than a glorified wire wrap... it develops a break in the wire...when it's cold it makes contact. Heats up..expands and presto..no connection.

It's one of the most common things on a SC's W body. I pulled up to the neighbors house... got back in the car it started and stalled. Started and stalled again, I got out, bent the tab and since that day this summer, I haven't touched it.