325 overheating

My 325is started getting hotter that it normally gets. The gauge never goes beyond half.
Now it swings between half and 3/4. The coolant system was flushed and serviced by the dealer 5000 miles ago. The coolant level is where is should be hot and cold.

Any suggestions?

Thanks

Same thing happened to my 3 series one day I noticed the needle was above normal and I ignored it until it finally overheated. and I had to get a new radiator, according to my mechanic he said my thermostat was clogged causing the car to overheat, you might want to get that checked.

I took it in, they replaced the water pump and the t-stat. The impeller was destroyed.
1996 and earlier E50 motor came with a water pump where the impeller was plastic.
The dealer relaced it with the newer metal one. The t-stat was replaced anyway.