4runner dies at idle help please 2003

[toyota970]

I cant seem to wrap my head around it. i was sleeping in my truck at work. when i woke up engine was completely off. battery light and park illuminated. went to restart no noise or click nothing. got it jumped truck turned off at stop sign 40 seconds later. wouldnt start again. came back 2 hours later and it started like nothing was wrong. the problem keeps happening its fine getting straight to a place and thats it. but let it idle and its dead. ive changed battery still no change. the alternator and battery have tested fine at advance auto and dealership. im taking it up to dealership and getting timing belt replaced shes at 86,000. so im changing alternator also since its gonna be offand no extra labor cost. does anyone have any insight on this im really stumped. also put a can of seafoam just because i thought maybe there was some water in my gas. no chnage. also my headlights and everything elsework fine with all this goin on dont dim or anything