Yes, it will trigger each time the condition is met until the spell ends
Some may imagine this abjuration spell turns the 25 feet of rope that is the consumed material component into an invisible, animated rope, such that once the rope is hoisting one creature, there is no rope left to hoist a second. That is how I pictured it when I first read the spell.
But this is not what the spell says.
When you finish casting, the rope disappears and the circle becomes a magic trap. (XGE, 165)
It does not say that the rope becomes invisible (which is how I had misremembered it). The rope "disappears", being consumed by the spell. And the "circle" on the floor that the rope bounded "becomes a magic trap", rather than the rope itself becoming a magic trap.
The trap triggers when a Small, Medium, or Large creature moves onto
the ground or the floor in the spell's radius. (XGE, 165)
So the first creature enters the circle, fails their dexterity save and gets hoisted into the air. But the spell has a duration of 8 hours. Unless that time has elapsed, and so long as the following condition has not been met, the spell has not yet ended and is still active:
After the trap is triggered, the spell ends when no creature is
restrained by it.
So will the spell trigger again on a second creature if one is already restrained? There is nothing in the spell to indicate otherwise.
Let's compare with a couple of other abjuration 'trap' spells that are triggered by certain conditions being met. The 3rd level spell Glyph of Warding has a duration of "until dispelled or triggered", meaning that triggering it once unleashes its effect and then there is no more Glyph. The same is true of the 7th level spell Symbol. But unlike these two, which explicitly say that triggering the spell causes it to end, Snare simply has a duration of "8 hours", which means it continues to be active after triggering, so long as nothing has occurred to cause the spell to end (i.e. eight hours have not yet passed, there is no creature restrained by it, and no one has cast Dispel Magic).
It seems entirely possible that a well-place Snare spell could end up restraining, for instance, a whole herd of sheep (imagine them being herded through an open gate that had Snare cast across it). Or if you had a trap or effect that pushed an entire party into or through a five foot radius circle, the whole party could get restrained by a single casting of this spell (assuming they all failed their Dexterity saving throw). Note, there is nothing in the spell to say that the movement that causes a creature to enter the circle has to be voluntary (compare the cantrip Booming Blade, where the extra damage only triggers if the target's movement is voluntary).
Superfluous Personal Commentary
This is a much more useful spell than I had realised. I think it could make an excellent trap when combined with, say, a collapsing floor trigged by a certain amount of weight (e.g. over 500 pounds), which opens over a drop that has a chute that spits the victim(s) onto a spot on the floor below that has Snare cast upon it.