Vapor Lock?

I am a new member who has recently purchased a 1979 450SL. I purchased the car approximately 200 miles from my home. 150 miles on the trip home the car died while I was traveling at 70 MPH. After pulling to the side of the road I tried to start the car. It would turn over but not start. I continued doing this over a period of thirty mintes. Each time the engine came closer to turning over and starting. At the time the tow truck arrived the engine turned over and started.
The next day the car started and is running smoothly, but I have no confidence in driving this vehicle for an extended time.

My questions are:

Has anyone else experienced such a problem?
How was it solved?
Could this be a vapor lock problem?
If it is a vapor lock problem, what is the cure?

Looking forward to reading your opinions.

Thanks,

Cookie 79