The methodology is the same as a previously posted thing, but the copy-to-points node needs to be situated inside the For Each loop

if you squint, you'll see there's an attribrandomize node. I've made an integer attribute called TimeOffset and ..randomised it..
In the timeshift node, I make a spare input and point it to ../PT, which holds said TimeOffset values
The value for the timeshift is : $FF+point(-1, 0, "timeOffset", 0)
so, we take the current frame and add the individual time offset value to it.
Shweet.