From your description, it sounds to me typically like the solenoid. One thing you might try ...when the truck won't start, rather than pop the clutch to start it, instead disconnect the positive battery cable, then reconnect it. If the truck then starts up, it's the solenoid. The solenoid can stick intermittently without engaging the fly wheel, but disconnecting the battery will allow the solenoid to drop back down. You may have to repeat this battery disconnect several times if the solenoid is sticking repeatedly, but if the truck finally starts this way, then it is the solenoid that is bad.
As long as you are hearing the "buzzing" sound, and then it eventually starts, I would bet it's not the battery or battery connections, since the battery will start the truck after you pop the clutch & then turn it off & restart it. A short in the ground cable is possible, but not likely from your description of the problem. Just my $ 0.02 worth !!