You have already picked excellent fund companies. Of the three u mentioned, Fidelity & Vanguard have an enormous variety of mutual funds to choose from (T.Rowe Price has excellent funds, but far fewer in variety.) Also, Vanguard has been & continues to be the fund company with the lowest fees overall, although Fidelity is certainly trying to compete hard there as well.
Since IRA money is for ur retirement, & thus for the long-term, u should not be too conservative with it (no CDs, for example). This argues for a high % of stocks or even 100% stock fund (depending on any other investments u may have, that u did not mention).
Shana is suggestion of one of the target retirement funds is fine. These do tend to be quite conservative but the percentage allocated to stocks drops over time (as u near retirement, which is advisable). The Fidelity & the Vanguard target retirement funds differ in their percentage of stocks for a given retirement date, but r very similar.
But if u have no other stock investments, u could easily go for an S&P 500 index fund, which invests ur money in 500 of the biggest US companies. (And thus is well-diversified among US companies.) Alternatively, look for a 'total market index fund'. Both Fidelity & Vanguard have both of these types of funds.
Whichever u pick, do not judge it by any short-term fluctuations. The market fluctuates, & the ups & downs r important to short-term traders, but considerably less important for ur long-term needs.