Bite the bullet and pull the transmission to see what you've got bound up, because something is definitely bound up between the crankshaft and transmission. If you can't turn it with a wrench on the crank pulley bolt, it's never going to spin over with the starter.
No transmission/torque converter connected: engine spins freely
Trans/TQ attached: engine won't spin
It's pretty obvious something isn't attached correctly.
Quotes to live by:
guessing gets expensive
nothing is more expensive than a cheap BMW
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito)
Ken Kanne, Silverhill, AL, E36 Forum Mod/Craigslist addict/Hoarder of all sorts of stuff
1995 318is "Bebe"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette"