Car won't start

I have a 1994 saturn, 1.9 twin cam. 175,000 miles. It was running fine until 2 weeks ago, then when I went to start it nothing, no noise, no clicking when I turn the key over, wait about 20 mins and then it would start and would continue for days. This happened about 4 times now it did it again and won't start at all. Like I said turn the key over and nothing. Is it the starter or what? If it is where is the starter located.