Safest place for retirement savings?

I have some money in a retirement accout from my previous employer. I am retired now but don't need to start taking disbursements for another 6 years. I am very worried about the stock market as I lost about 25% with the last downturn during COVID. Is there anyway for me to prevent that again without moving to a savings account and paying tax on the whole amount at once? Can I keep is safe and leave it with Vanguard? Thanks in advance for any suggestions.