Car turns off while driving, restarts no problem

1997 pontiac bonneville; 150,000 miles - increasingly often, my car will randomly turn off while driving. It generally doesn't happen while I am pressing and accellerating. It's happened once coming to a short stop, a few times while idling at lights, and most commonly while driving at a steady pace, pressing the gas but not increasing speed.

when it shuts off (dies) I put it in neutral and restart it without any problem what so ever. If I press the gas immediately afterwards, it makes a sound similar to something in a metal can being shaken around.

the car doesn't have any major issues, except it needs a new serpentine belt. Could this be related to that?