possible Alternator issue?

Check the thick wires (BATT & ALT) in your bulkhead connector. If melted (common), search "MAD Bypass" in the Electrical forum (where this question should be).

It wouldn't be your alternator, since your car could run fine for 100 miles on battery alone. But, buy a cigarette lighter voltmeter to monitor while driving ($15 Amazon, cheaper LED type at Harbor Freight).