Intermittent trouble starting my 1999 Toyota 4runner

Every once in a while first thing in the morning my car will start and then die on me. It is random, but more likely to happen in damp weather and cooler weather ( cool for Florida), and when the gas is low (1/4 tank) but not consistently. I put in engine cleaner and that seemed to help at first, or placebo effect. Every mechanic I speak to says they need to see the car when it happens. This is not practical b/c it does not happen every day and only first thing in the morning.
Recently, after driving 38 miles on the highway when I stop at DD for coffee and the car has been dying as I go through the drive through and the light after. Not sure if it is my imagination, but it seems to do better if I turn off the ac. The car is a '99 4Runner. Any ideas?

Many possibilities. This one ended up being bare wires from the fuel pump:

Since it runs better when you shut off the AC, look for the ground wire that grounds the engine to the body. It used to be a good cure for a Toyota in the 1970s, not so much today. I used to disconnect the body end and wire brush it then scrape the paint off the firewall and reconnect the wire. Problem gone! The engine would also turn when you turned the key. Handy when that happens. It would also be handy if this cure would work on a 99.