Because of the hot battery cable or cables a heavy intermittent short is present at times. The starter is the best suspect but hard to prove sometimes when intermittent.

I do not think a shorted alternator would normally clear itself. Also the next time it happens I would take a meter to make sure the glow plug circuit has not remained on. This glow plug current draw though substantial would not heat the battery cable I suspect though.

The described senario is very hard on a new battery. After you locate and eliminate the problem you might want to take your fairly new battery in for a test. Todays batteries have little tollerance for this kind of treatment.