My SAAB randomly won't start

After four trips to the dealer, my 2002 Saab 93 has the same problem: It will randomly just stop running (while driving). At other times, it just won't start at all, after I've been driving it around all day. It may run great for a week or three, then out of nowhere, it gets an attitude. The battery is new (in addition to many other parts in hopes of correcting the problem), all the lights come on, everything works fine, but when I turn the key, it sounds like it wants to start, but it just won't turnover. If I wait a while - anywhere from 5 minutes to 55 minutes - it will eventually turn over, although it struggles to do so and I have to pump the gas peddle over and over and over. Mechanic now wants to try replacing the throttle body. This is getting expensive, and each time the mechanics try something new or replace something, it will run great for a few weeks, then BAM, and we're right back to the original problem. My friend thinks it's not getting fuel. But it that's the case, then why does it run great some days and then won't start out of the blue?