Before u get the car into a garage to check the fault codes ( may be an expensive trip unless they do it for free ) I would go get a free battery / alternator test from your local motor factors.
Sounds very much like a loose lead or faulty alternator diode.
You can check the batt terminals yourself by removing the plastic trim at the front passenger side of the engine bay..
Excusing the scribble here's a pici
Also, make sure the battery cables are fastened securely and not corroded. If you find corrosion around the battery terminals, clean the terminals and the cables thoroughly. To do this, just mix a little baking soda with water and use a toothbrush to carefully brush around the cable connectors. If corrosion is excessive, replace the cables. Make sure you dry the area before starting the car.
Hope this helps