Spider starting problem

[RPI1@domain.elided]

Greetings all. I have a starting problem with my '79 Alfa Spider. The problem 
is intermittent, and I can't seem to find a consistent pattern. It does seem 
to have problems more often if the weather is very hot (90) or very cold 
(30-35). 

I have had two mechanics tell me the charging system and the battery are 
fine. I had a new battery put in anyway, out of pure frustration. Didn't 
solve the problem.

When it won't start, there is absolutely no sound. No clicking. No slow turn 
over. Nada. The headlights and dash lights will work fine. 

If a I put a charger on the car for 5 or 10 minutes it will start. If I get 
someone to give me a jump, it will start. 

This is the most recent thing that happened. I was driving (highway) for 
about an hour with the lights on. It was afternoon, but cloudy. About 55 
degrees. Parked the car, fed the meter, and realized the lights were still 
on. Shut them off and went to do so some errands. The car sat for about a 
half hour. Wouldn't start when I came back. I put  a voltage meter on the 
"dead" battery, and it read 12.79. I called a friend who came a jumped it, 
and it started right up. I parked it at his house overnight. Started right up 
at 2 p.m. the next afternoon. 

I then drove the car for an hour and a half (highway) with the radio on, but 
no lights. Parked the car until about 10:30 p.m. It was about  35 degrees 
then. Car wouldn't start. Got a jump, and it started fine. It's been parked 
in the garage the last couple of nights and has started fine. Garaging does 
not guarantee starting, however. I did have a small scare this morning. Drove 
it to church. After church I turned the key and there was no sound for a 
second. But then it kicked over.

Any suggestions about where the problem is? Thanks.

- --Nick W.

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