I've posted about this in the past but never found the problem. It's gettin much worse.
When attempting to start the car it won't. It acts as if the battery is dead. After which there may be no noise or clicking under the hood sometimes in the trunk and sometimes the security light near the shifter flashes. Sometimes I know it's going to happen as soon as I get in the car because the courtesy lights are dim.
I've checked all possible loose connection that I've been told may be the problem. I drove the car to a garage to have the battery and charging system checked. Yesterday I went to start it after it gave me a problem the night before and I put it on the battery tender thinking bad battery. Disconnec the tender got in and noticed dim lights right away and it won't turn over,nothing. Took the battery out and brought it to the garage where it checked out fine.
Every time it happens I do the hard start touching the positive and negative together for at least 10 seconds works every time. I carry a 10mm wrench with me now.
Please help lol.

 

My 98 XK8 will do something similar once in a while. I haven't notice any dim lights, but occasionaly when I turn the key to start it, the dash lights come on but nothing happens, no click, no dim lights, nothing. Turn off the ign, then retry, and it starts fine.
Only once in the 10 years I've owned it have I had to disconnect the battery to correct the problem, but just like you I carry a 10mm wrench, just in case.
I'd like to know what the cause is too.
Regards,

 

Sounds like a faulty starter solenoid to me. Over the years I've had four vehicles do the exact same thing, some days start first time, some days start on the second or third time.
Land Rover
Lincoln
Trailblazer
Impala
In all four cases it turned out to be the starter solenoid. However, it could just be a loose wire at the starter as well.

 

Since going through the motions of the hard-reset procedure gives you a temporary fix, I'm very suspicious of the battery terminal connections, the ground strap, and/or its connection to the chassis. (The hard-reset itself should not produce the results you're seeing.)

I'd work through those spots carefully. Next time the problem returns, see if you can detect any looseness at the terminals. Try just working on reseating and snugging things up there without the reset procedure to see if that also gives you a temporary fix.