I had an intermittently bad alternator do a bunch of things you are describing and worse, chased the problem around for months. sometimes the truck would just blow a 40amp fuse as soon as i keyed on and i couldn't drive the truck for a week or two then it would be fine. One day i took it on a 4 hour road trip with no issues and when i got home a ton of smoke came out of my alternator and all the dash lights went on again and my voltage dropped on the gauge. After that i replaced the alternator and never had a problem again.

Not saying that is your problem but it's something to check out.