It sounds like your battery is weak or slightly discharged. You mentioned that it's only 4 months old so it's most likely not a bad battery. You more than likely have an electrical draw somewhere in your vehicle that slowly drains it over a period of time.
I would start by performing this quick battery load test(see link below), just to make sure we don't overlook the possibility of a bad battery(sometimes they are defective). Any local automotive parts store will also test your battery free of charge if you're more comfortable with that.
Assuming the battery passes the load test, the next thing you need to do is determine if there is a draw with the key off. The link below will walk you through this process.
Let me know what you find!
Thursday, September 12th, 2019 AT 6:50 AM