Sounds like a battery problem....barely holding a charge. Also get your alternator tested. If you have a volt-meter or a multi-tester do the following:
Run the engine with NOTHING electrical turned on...no lights, no stereo, no heater motor blowing, no wipers etc. Take a reading off the battery. This should be between 11.5 and 13.5 volts.
Keep the engine running and turn on all your electrical equipment except the wipers. So turn on your headlights, heated rear windscreen, stereo, heater on full blast. Take another reading and keep the tester on the battery terminals. The alternator should be doing its job and providing the car with the additional electricity it needs to replace that soaked up by all the electrical equipment running. Reading should be around 11 - 13.5 volts.
Keep the tester on the battery and if you see the voltage drop gradually over a couple of minutes you will know that your alternator is faulty.