[BDub]

I'm thinking your alternator may be failing or there is a crap connection somewhere. Crap connection would be my first suspect given the fact that it seems to happen suddenly and then work again later. I would load the system (AC on max, high beams, defroster) and do some voltage drop tests. Also, unless the voltage got so low that it cleared the memory on the PCM, there may be stored codes that can be pulled even though the check engine light isn't on at the moment.