hard to get the starter to engage

I have a 99 jetta 2.0. I don't know anything about Volkswagens but need to figure it out. Its hard to get the starter to engage when you turn the key. Usually takes 2 or three times, then it does. It sporadically stalls at stops and sputters when only going up to 40 or 50. And sometimes at 70. But acceleration is great and has lots of power. Only has 96000 miles on it. It runs fine a week or so then starts its crap again. Only the starter situation is all the time. Ive read one forum that says these main relays are a common problem and need to be upgraded due to being too week for the heat. Is this possibly whats causing both issues seeing that it controls everything? Thanks