I had this exact same problem about 2-3 years ago on my 2000 4Runner. I would start it up, and almost immediately, it would shut off, as if the fuel were cut off. Even if I gave it gas immediately after starting up, it would die as soon as I let go of the accelerator. This would happen intermittently, so it was quite frustrating, especially when it would happen when I was far away from home. At first, when I took it to the dealership, they said there was nothing they could do unless I could replicate the problem, but sure enough, as I was about to leave I started it and it died right in front of the service advisor (what luck!). It turned out to be a faulty THROTTLE POSITION SENSOR (TPS). It was replaced, and I haven't had the problem since (2+ years). Hopefully cleaning the MAF will do it for you, but if the problem comes back, you might want to test your TPS.

On a side note, I had my 4Runner shut down while driving just like you tonight. The check engine light came on while I was on the highway, and as I got off, I was cruising about 30 MPH when the engine just completely shut off without warning (RPM went to 0 and all warning lights came on) and I coasted (luckily, safely) to the side of the street to a stop. I was able to restart it, and it seemed to run OK, but the check engine light is still on. I'm going to try and clean the MAF and throttle body tomorrow, but I think there's a good chance I may need a new O2 sensor (hasn't ever been replaced). Please keep me posted if you solve your problem.