US stock markets are generally open for trading between 9:30 AM and 4:00 PM (ET). Many people believe, me included, that the first 1 or 2 hours after open (9:30 AM to 11:30 AM ET), and the last hour before close (3:00 PM to 4:00 PM ET), are when there’s opportunities due to chunky trading volumes.
Fire up a platform and look at Nvidia as an example. You’ll see lots happens in the first hour and a half ish as momentum traders and institutions flood in.
I’d swerve lunchtime hours (11:30 AM to 2:00 PM ET) because you’ll see volume drops and you get choppy price action.