2000 Mercury Cougar complete ly dies to the point of getting no spark at battery post

So this has happened twice ( a month apart ) and at very random times. One time just turning around on a dirt road all of the sudden car goes off. Open the door and the dinging noise when you door opens sort of comrs on but extremely faint so I get out pop the hood and I yanked the negative cable off and then retouch it to the post ( there should be a click or mini zap or sound of connection) no sign of connection whatsoever . So im thinking battery iscompletly died out for some reason so I go get a jumper pack but b4 I put it on I go and try the touching the negative cable back to post and what do you know, sign of connection and I get in the car and she starts up and acts like nothing is wrong and it has worked normel ever since until sunday two days ago coming home from watkins glen. went to the nascar race at the glen and was driving homea ( alot of drdriveing that day 2 hrs there and back and I was speeding alot in excess of 110mph on a few occasions) car worked normal all day and like 30 miles from home all of the sudden im doing 60 and all the dash lights come on and the car completly dies sorta like symptoms of an alternator dieing but extremly accelerated so I know its not the alternator. So I throw it in neutral (mtx by the way) and coast to a stop. I turn the key to on and try accessory stuff like radio and the car shows no sign of life just like ladt time basically. So I get out and do the touching of the negative cable to post thing again and just like lastime NOTHING. . And so I just sit there for ten minutes scrathing my head and thinking and then I try one more time like last time, touch the cable to post and I get the click of connwction and get in the car and its been working well since sunday BUT I WOULD LIKE TO KNOW WHAT BLOODY HELL IS CAUSING THIS!!! Just a side note my gas guage doesnt always work properly it will read empty when the tank is full but fix it self and go to correct position it judt goes out intermittent ly but I dont think its related to my possessed electrical nigjtmare or whatever is killing my car at random

You have a bad battery cable or a bad ground. I’d start by cleaning the terminals and connections to it.

Then, if that doesn’t work, get a booster cable and, USING ONLY THE BLACK LEAD, tie one BLACK end to the negative terminal and the other BLACK end to any bare metal piece on the engine. Do NOT use the red lead at all.
If you can now start the car, you have a bad ground somewhere - very likely from the battery to the frame since when you jiggle it, it comes to life. Move the one you had clamped on the engine to the frame. If it now still is alive, your problem likely is between the battery and the frame.
Should, after moving the wire, the car have problems, move the cable between the frame and engine. If it now works again, you have a problem with your ground between the frame and engine.

Basically I’m suggesting you bridge the ground connections using a booster cable to help you find where your problem may be.

Okay thanks ill have my mechanic look into my ground connections I dont have the patients to diagnose that bs lol

I am going to warn you about your practice of looking for a spark at the battery post as a diagnostic tool. One of these times, you’re going to get a face full of acid when the battery blows up in your face. It hasn’t happened yet but the risk is high.

Ill continue to count ny blessings;)

If the battery ground cable proves out to be okay then check the positive side of the battery. There should be a smaller power wire coming from the battery post or the battery side of the starter solenoid that ties to the power panel under the hood which supplies power to all of the electrical systems of the car. Moving the wires around while watching the dome light may lead you to the fault.

The trouble could be with the ignition switch but if things like the courtesy lights and brake lights don’t work when the trouble happens then it means the fault is before the ignition switch and points to the panel and wiring located under the hood, close to the battery.