What do you mean when you say that your iPad Mini doesn't charge so well? Do you feel as if its taking too long to charge? Does it ever reach full charge capacity? Is your charging cable frayed or is possibly damaged? have you tried using a different charging cable? Anyway, if you've tried various things to make it charge to your satisfaction and it still does not or you feel as if you may have a defective unit and if you are near an Apple Store, make an appointment to have one of the geniuses look at it and maybe even swap it out for another one.
Mine hasn't restarted once so idk what exactly is going on, maybe if you gave some more information people could help but with what you posted it's kind of hard to figure out what problems you are having.