92 500E throttle problem..please help

[vcci]

i have recently bought this 92 500E, I have been a big fan of the 500 for a long time and finally bought one. Now that I have been driving it for a couple of days I notice that from time to time the car will lose the throttle, I could be on the freeway and out of nowhere its like there is no throttle response unless I push it to the floor. It has happened to a friend of mine along time ago on a 92 400e, any idea as to what it can be or what I should check first. It tends to do it at any spped and for no reason, sometimes it wont do it for a while. Any help is greatly appreciated.
Thanks