in 1996, the 3.0 Mitsubishi engines eliminated the optical distributor and replaced it with a Hall-Effect pickup. I've not yet heard of a HE distributor pickup failing on a 1996 to 2000, 3.0 yet. They seem reliable.
One possibility that comes up from time to time on these engines is a bad crankshaft position sensor located on the transmission bell housing. For some reason, these tend to fail or become intermittant when the engine is fully warmed.
You should be getting an error code for a sensor issue, so if you are not, you may be in the early stages of a fuel pump failure, assuming at 225,000 miles it has never been replaced. These pumps have internal DC motors that use carbon brushes that will evenually wear down to become intermittant and ultimately cause total failure.
First determine if this is a loss of spark or fuel or both. A road test with a scan tool or data recorder and a helper may help to catch the culprit.
It probably has to occur in order to find it if no fault codes are being left behind.
A fuel pressure gauge and hose can be tucked under a wiper blade for observation while driving. Make sure that there are no fuel leaks before starting out.