Error: Start-stop (BlueGT 2017)

[Volkswagen]

Hi,

Two days ago I started my BlueGT 2017 (60300 km / 37500 mi) in the morning. I felt that the engine was not running well, causing "shaking" feeling in the cockpit. Soon after this the yellow engine light started blinking, and there was a text "Error: Start-stop".

A day before this incident, I drove about 70-80 km/h (43-50 mp/h) and I felt this "twiching" feeling when driving this constant speed. The feeling was like the car going "back and forth". I have DSG.

I called technician about this, and he said it might be the battery because I haven't replaced it since 2017.

I still wonder why there wasn't any battery sign light, just the start-stop if the problem is the old battery.

NOTE: The yellow engine light and the "Error: Start-stop" text are not constantly there, I started the engine again today and there were no signs of them.

Any other possible reasons for the yellow engine light and "Error: Start-stop" text?

Thanks in advance!