Generally it's not a good idea to try to time the market. You're playing with your retirement savings, and chances are that you'll end up making money if you put your money in the market now and hold till you retire.
If you think the market is going to have a substantial correction soonish, you could look into volatility ETFs. They basically go up if the market goes down.
I'm in SPXL (which is a 3x leveraged ETF i.e. if the S&P goes up 1%, SPXL goes up 3% and if S&P drops, SPXL drops x3). You can get leveraged volatility ETFs which can go up by 2-3x if the market drops. I haven't, but you could put some money in those if you think the market will drop and you'll make a good bit of money.
I'm up ~50% in SPXL and ~60% in TECL since January, but if you want to bet there's gonna be a correction then throw some into volatility ETFs, just don't hold onto all of your savings in cash.
A large chunk of your savings into a market tracking ETF, and then some in riskier buys like leveraged ETFs might be a good way for you to ensure you are protected if the market goes really far in one direction really quickly.