2004 subaru wrx impreza

Weak battery. Have the battery and alternator tested.

sounds like a low charge in the battery.give it a full charge,preferably an overnight trickle charge for best results.if you have a multimeter check your battery voltage before and after the charge.also clean the battery with just hot soapy water before you charge it, most people don't realize that dirt and dust along with a little condensation is conductive across the surface of the battery, and will slowly drain your battery.DON'T use baking soda on your battery.after completing the charge it's more than likely got a pretty high surface charge which can cause an arch when re-installing the battery,not safe for you or your vehicle.but if it's 15 volts or more after charging just use some jumper cables and connect one end of the cables up to your battery like you normally would then just tap the other end of the cables together just once real quick AWAY! from the battery. if it starts ok then I would check the output of the alternator,preferably at the alternator and then at the battery ,any difference between the two is a volt drop like a bad connection,corrosion ect.optimal voltage is 13.8 to 14.2. good luck

It's just a battery. Subarus are tough as a rock.