Can ETFs been used to buffer idle money?

Hi don’t know if that title makes sense but basically, I am a trader that's been actively engaged in my portfolio for a while but sometimes I have lumps of cash that are sitting around not in anything while I'm looking around for a stock that I want to invest into. I want the money to be put to good use while it sits there so I wanted to know if ETFs at any point are good to put money into and let sit for an x amount of time (probably not longer than a couple months or less) until I needed it, for a trade I'd rather be in. I know ETFs are usually the safer way to invest but I like the active trading style so if prefer to not, I just don't like seeing my money sitting there doing nothing