My truck battery randomly dies?

Every now and again I go to start my truck and it is dead. There is no pattern at all. It can be dead and then I'll jump my battery and it might be fine for a week or more. Some times it doesnt even take a day before it is dead again. I am not leaving anything on and i have no reason to believe power is being drained by something staying on. If I go a day without running my truck the battery is almost always dead. Recently my truck died and I jumped it and it was dead a few hours later. I jumped it and ever since when I start the truck all of the gages act like the truck was dead. They all flutter and make ticking noises before showing normal readings like the battery had a low charge. The truck never goes completely dead. It just doesn't have enough to start. I'm hoping it may be the battery going bad. But I fear that the gages fluttering and ticking means there is a delay in the truck starting and the starter may be going out. i really cant explain the situation much better. My truck is randomly dead, there is no pattern. I can go a month with no trouble.. Sometimes a day.. Just last night I turned on the cab light for mayb a minute and a half looking for something and the baterry didnt have enough juice to start the truck after. Any thoughts? What plan of action should I take to isolate the problem?