PAS problem when red battery light comes on?

Recently I bought a Saxo VTR, naturally there are several minor teething problems. When i start the car in the morning the PAS seldom works, combined with the battery warning staying on. However if i turn the lights on and off this cures the problem and the PAS is ok. So far car always starts in the morning never sounding sluggish or anything like that, the drive belt is a tight as it should be, and all terminals on battery are secure, whilst this is ok on a short term basis,what really is the problem, which i'd rather treat rather than suffer breakdown, non-starting or worse an accident in the future? Thanks for any advice. iain