It can be an actual overheat, caused by a thermostat, fan problem, etc, or a sensor failure, which looks just the same.

Given the high cost of resultant engine damage due to overheating on these engines, I would keep a close eye on it.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue