Vw 91 Jetta Problem Please Help!!

I have a vw 91 jetta that pretty much everything else in brand new underneath the hood because of this problem that i can't fix. What it does is if the car is driven for a long time (30 min at 70 mph) and then i park and turn it off, it won't start for like an hour or maybe a couple hours. It's almost like it needs to be really cooled off or somethin. My starter doesn't even turn over, just my radio and lights turn on!!!
Somethin i've noticed though is if i put a battery charger on it for like 2 min it will start up no matter how long it's been sitting. I could sometimes drive a lot longer but the longer this problem goes, the shorter distance i can drive without it not starting, PLEASE REPLY IF YOU HAVE ANY IDEA!!!!
THANK YOU

you jsut solved your own problem from what i see it is 1 of 2 things 1 you need a new battery 2 you need a new altinator sorry for the misspelling