2002 Pontiac Bonneville Loses power when driving

My guess is you are losing spark, or ignition voltage. Do you get any check engine light during this, or has it been checked for any stored codes that would give an indication?

That would suggest that it is probably a loss of ignition voltage, at the same time the PCM could be losing the voltage for running, it is also losing it's capability to set a code. It may be similar to key being shut off, and can possibly be the ignition switch that is causing it. You could possibly backprobe and check for losses of voltage, this could be a process of elimination, and time consuming depending upon how often it occurs. Otherwise, duplicating it with a scan tool that can read data installed, is another choice.