Starter relay or no starter relay, Been reading up for an hour and still don't know!! Options

[David Stowers]

On two occasions recently on pulling onto my driveway after a long journey my car won't restart after turning off to unlock the garage door. Luckily I can then just push the car in but with a European tour booked in the summer I'd like to sort the problem.
When I get back in after opening the garage the lights on the dash dim when I turn the key to start but there is no click. 20 minutes later it will start right up. Is this the problem that will be solved by a hot start relay kit or just a good old fashioned sticky solenoid? I'd rather do just the relay or just replace the solenoid so which is it?
Thanks guys

[Tom]

The inductive spike is what makes the arc and carbon build up. The tiny spark from a relay that draws 150 Mili amps is really small compared to the arc from the 35 amps the solenoid draws. To determine the voltage, use V=IxR, where the resistance of the opened contact is meg ohms. 35/0.150 = 233.3. So the spark from the solenoid is going to be 233.3 times as bad to the contacts.
The switch is only going to have so many of these events before the carbon build up or surface damage from pitting causes a high enough resistant connection in the key switch and the solenoid no longer operates, then either a relay is needed or the switch requires replacement. Installing a relay will prevent early switch replacement.
I have done this test several times to convince others of the reason switches fail and if I had a camera that would take video, I would post one here. It is eye opening!!
Tom