I noticed that the battery light on the.

I noticed that the battery light on the dashboard recently started blinking when starting iver the last 1 week. Blinking stops after a short while when driving. Blinking is getting more frequent now but yet again it stops after driving for a short while ( about 10 to 15 minutes time ). Everything works fine, car has no issues and no problems with speed or power. Car starts normally. Not sure if it is an alternator problem or the belt. Appreciate if you can help. Thanks.