So this is an odd issue, but my E36 will start fine in the morning of after a decent period of time (3-4 hours) with no issue. However if i try to start it soon after running the car for a little it will begin to crank then proceed to a loud vacuum noise coming from underneath the car. I took it to a shop recently and of course it starts fine when they check it. Some days itll start fine over and over however some days ill barely be able to start it after my first start in the morning. Any ideas I can tell my shop? Thanks