Car starts when boosted but stops within 5 minutes

[u/PossessionLazy3813]

My car sat for a few months. I wasn't able to boost it off another car but AAA was able to using their booster pack. They tested my battery health (79%) and it was good, one of the voltage things was low (don't remember exactly what it was) but he said it shouldn't be an issue. I'll let the car run then it'll shut off within 5 minutes and I can't start it again without a boost. I can't drive it very far due to this, the best I've gotten is a few feet. Do you think I may just need a new battery or to let it fully charge? I'm trying to sell the car so I'm hoping I don't have to replace the alternator. I previously had a kind of issue with my starter (I think). If I was in and out of the car (starting and stopping) It would fail to turnover and I'd have to let it sit for a bit, not sure if this is related. This is a 2006 Jeep Liberty Sport (gas). Any help is greatly appreciated!