fuel engine stalls gauge

Hi all from NZ :-) Have a c200 97 4 cylinder - bit of an odd fault - wondered if anyone had any idea's ? Battery was flat so charged up and ran fine for 50 km stopped for 5 hours went to start and it caught but died like no fuel went to start again and nothing rested it for a while and it...

My W203 2001 has been having this problem of switching off even if the fuel gauge is at half. I just have to add as little as 5 litres and it starts then and runs normally. The gauge isn't really faulty as indeed there is fuel in the car as all I normally need to top up to fill the tank...