87 sierra

My 87 sierra is becoming very hard to start. However, once it does start it runs pretty well. My mechanic told me he didn't find anything and thought it needed a new throttle body. Would it need a TB if it runs well after finally starting? What about a throttle position sensor? Does this have anything to do with hard starting? Even a rebuilt TB is very expensive. Any ideas? Help!

Welcome to AF, vague desription here, many things can cause this, weak spark, restricted fuel filter, low fuel pressure, worn plugs. The TB would only be an issue if the press reg was bad or the injector seals leaked.