My 2000 528i has trouble turning over atleast about once a day..it eventually cranks on the first try but takes awhille. Wats wrong?

Take the car into auto-zone and have them preform a check on the battery . It is called a load test . It will tell you the state of the battery and it if free. If the battery is over 3 years old it might be time for a new one. And thy will test the other charging components at the same time

Do u mean it turn over slow & barely starts or turns over as normal but take some time to fire?

If it turns over slowly take the advice above & get the battery tested. l do not know about Autozone though. l try a place that specializes in batteries. Here l use a place called the Battery Exchange. Check ur Yellow Pages.
If the battery is tired be sure to replace it with a Johnson Controls product like Interstate & not an Exide product. Google Johnson Controls to see their range of battery products. The battery in a BMW is not a place to get cheap.

If it turns over as normal but does not fire immediately then it is probably the check valve in the fuel pump. You have two options. Replace the fuel pump ($300) or install BMW is retrofit designed for the 750iL ($15).
It is an external check valve that installs over the fuel pump & takes all of 30 minutes.
Part number 16149068988 right from BMW.

Your starter may not be the problem if it doens not even click when you first try and it does not crank. You many have a bad SLOW ignition switch its more common than you think.

If it sort of cranks , but seems like it is not catching (you have to turn the key back to off and then restart . Then it is your starter . It is relatively inexpensive to replace yourself , just a little bit of work ;) . If it is slow to start (you have to hold the key in start position for several seconds before it starts) then it is likely the battery, which is rather inexpensive and easy to do yourself . good luck

Go to Walmart. They will check your battery for free. If its the battery,great! You got away cheap,which l believe it probably is.

As the other is state, get the diagnostic code before you replace the battery, starter or alternator.

There is a electronic part called the ''Final Stage Resistor'' that may be draining the battery. It happened to me.

When you go to start the car it goes ''click click click click'' and then the next time it starts right up.