07 Tahoe. I have to bump the ignition switch several times to get it to crank. It fires immediately and dies within a second. It does have throttle response for that second. Security light is not flashing.

Backstory: One day, guages started flickering, doors were locking/unlocking on their own. A day later, the Tahoe had no power at all. Set new battery in and connected and it fired right up. Locked down battery with the battery strap and it would not crank again. Wiggled cables at the ground end and it was fine for months. It began acting up again so I replaced the ground cable and attachments to the frame. Now it will do the previously mentioned. Gushes are bright, windows are speedy, windshield errors function properly. I have to bump the starter several times before it will crank. It fires and immediately dies. Pumping the throttle does throttle up. I am at all loss on this one. Any ideas?

 

Have you tried testing the vehicle with a tester that plugs in on the left side under the dash ? ( to see if there are any errors listed)
I won't say that THIS is what it is, BUT I bought a haunted vehicle and in years of driving it , it has Fd with us pretty regularly. The stories I can tell are like a stephen king novel + will raise the hair on the back of your neck, but in your case, it's likely electrical in nature.
my first inkling would be to clean all grounds first, on everything that needs to be grounded and use dialectric grease to them, to rule that out.