Hello and welcome to the forum. Looks like you have found yourself a very nice low mileage Z3.
Things to look for as per your intro post.
Common issues, at the age of these cars, include:
Worn dampers
Deterioration of suspension bushes and hoses on cooling system
Splits or cracks in rubber air intake hoses
Failed thermostat - car does not reach mid range on gauge
Rust on front and rear edges of sills - check underneath
Leaks from roof - check carpet carefully for dampness
Most things can fixed fairly easily and there is plenty of information on here to help you. If you can't find the information you need, just ask and somebody will probably have the answer.
It is also worth checking that routine maintenance has been carried out properly with oil, anti freeze and brake fluids changed.
Although the gearbox and diff oils are "for life" many members have changed them and found they get better gear shifts.
Finally, get out and enjoy your car whilst the weather holds.