hi ,first off welcome and I hope everything works out.
the PO might not of had a good mechanic work on the X5, so I would go over what was worked on first.
if You change your oil use Castrol [makes a BIG difference with Your valves]oil flow is everything with these engines.
if the PO worked on the transmission find out if he use the right fluid and check the transmission radiator in the front passenger side
Also with the radiator and coolant, You have to use BMW coolant [BLUE] there is a oil in it that helps the water pump bearing and won,t rust out Your radiator.
And You might have to bleed your coolant system like the other guy said. You can look it up on google for the procedure . good luck, I been there done that, make sure the INDY know BMW other wise they will just do damage.