Check the connections at the alternator, and battery.

 

This may be just a weak battery. How old is the battery?
Suggestion is putting on a charger overnight. Then next morning perform a load test of the battery. If tests weak or fail, obviously replace it with a good quality one. If pass or marginal, recharge for full overnight again and see what happens the next day.

PS: is there gasoline in the tank?

 

Look up videos on testing battery, alternator, and performing voltage drop test. Your problem is most likely the battery, connections, or ground. Could be alternator regulator, but sounds like something with the battery.