I asked about your battery and alternator because you indicated that your lights dim when the truck dies. I can shut down my truck and the lights hardly dim at all. So it was sounding to me like your truck wasn't sustaining enough electrical power to keep it running. But if it starts right back up, that may not be the issue.

 

I just bought a 98 with the same issue. Its a known issue. First thing first, have your battery checked. It may seem fine, but the rams are funky. Next thing, check/clean the TB and IAC/TPS. check the plenum. Mine runs fine sometimes and not others. These are the steps that I will take on mine. Also check for vacuum leaks. If you here a hissing sound you have leaky vacuum. I will update this weekend on what I found with my ram. Hope this helps

 

A huge vacuum leak will cause crazy idle. You really need to be able to look at the sensor data. You had O2 codes. Do you know which ones?