Amen to what everyone else has already said because the randomness of your problems and their timing would seem to indicate the problem is with your primary electrical system (i.e. the battery) kind of cutting out and then back in again.
Check the battery terminals (for corrosion) and the wiring connectors at the terminals. Odds are they're the primary culprit in this.
Also, one thing you didn't mention is how old is the battery. Is it getting close to the time to replace it? A weak battery can still start and run the car but also cause all kinds of intermittant electrical problems such as those you've been having.
Believe me - I know - I've been there. On a 1983 Chevy Impala the only symptom I had was radio static which turned out to be caused by a dying battery too weak to run the car and the radio!
