1997 528i starting issues

Okay.. so im pretty new to this. i've read a couple threads before that have helped me with DIY's so i decided to give this a shot. hopefully someone will know the answer to my problem.

i have a 97 528. recently since getting cold outside ive had issues getting the car started. the car will crank but not turn over. you can hear that it wants to turn over. before this issue it also had loss of power, rough idle, poor fuel mileage. I've changed all the spark plugs, the cam position sensor, the crank sensor and cleaned the MAF. this has fixed the loss of power and the rough idle and imporoved the gas mileage. however when i try to start the car after its been sitting over night it will crank but not turn over. it does this until the battery dies, then i have to get a jump start. after several attempts of trying to start it will turn over. once the car has been running for a while, it will start up fine untill it sits overnight then same problem next morning. sometimes i have to listen for the fuel pump to prime and once its finished i can start it. ive taken it to several mechanics, no one knows what the issue is. i have a feeling it is the fuel filter or pump. what do you guys think?

thanks

Sounds to me like the pump or filter. I think you're going in the right direction. The filter is pretty easy and cheap to replace, try that first. Then go for the pump maybe. Just sounds to me like it's not getting fuel.