I would suggest that you start with the easy things: Check to see if the large nut on the positive terminal under the hood is tight...but, if loose, don't overtighten it for fear of breaking that post.
Next, check the large black plug that enters the outboard side of the driver's toe box. This plug comes off of the positive terminal mentioned above and is held in place by a hexhead bolt.
Check the ground terminal under the hood on the passenger side where it attaches to the frame...by the oil dip stick. While checking grounds, look at the one on the front of the driver's sidesill...just about 2 inches after of the left front fender well.
Finally, consider checking the connections at the battery itself...and, check the battery ground cable where it connects to the frame.
There are many other things to consider...including wiring to doors, seating of individual fuses, etc.
Feel free to call me if you like...317 402 9013
Good hunting !!