I wouldn't shy away from equities ...a simple, low-fee index fund. Maybe select one with a good dividend yield. I wouldn't have predicted the growth over the past few months. Who knows if it will continue or not. I thought about some movement to bonds, but with slightly rising interest rates, that's not too attractive.
Do you do a one-time, annual contribution vs. a steady amount every month or quarter? The latter gives you more confidence, of course, for dollar-cost averaging. In any case, as a long-term IRA, I'd still lean toward equities and play for the long haul.