No electrical power - everything is dead?

Since it does restart, there has to be a short or weak ground. Here is what I recommend you try. First, disconnect the battery starting with the ground. Inspect the battery terminals, making sure they are clean and in good condition. Next inspect the ground wire. The primary ground will go to the engine block. Remove it from the engine, inspect the wire, and clean and re-tighten it to the engine. Inspect the positive cable, making sure it is good, tight at the starter and alternator.

When you reinstall the battery terminals, start with the positive. Make sure both the terminals and battery post are clean and able to make good contact. Additionally, make sure the terminal is tight. Often times, they will crack from age and over use. The result, you can't properly tighten them.