Seat Ibiza intermittent battery light & slight squealing noise

I recently bought this car and noticed there was a slight squeal when starting off in first gear at a low speed. The squeal doesn't happen when I'm driving fast. It drives fine so I didn't pay much heed to the noise - thought perhaps it might have been dirt in the brake pads because it was a wet day when I test drove it. Sounded like it was coming from the rear. Anyway, this morning the battery light on my dash came on intermittently while driving. Could these two issues be related? Does anyone know what might be causing this? There was a slight shudder when starting the car this morning, that doesn't usually happen... It shudders now and again when reversing... I'm still under warranty and wondering if the garage perhaps didn't do a proper service as I had to have an issue with the tyres fixed recently!