It seems to me that, RAW, you could always use the trigger "If I perceive literally anything happening," and choose to ignore the trigger whenever you don't feel like using the readied action -- effectively triggering whenever you want. Is this a valid condition for the Ready action?
This might be a valid trigger, depending on your reading of the semantics of "particular circumstance". But it barely matters, because it's a spectacularly useless one. The rule says:
When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger.
Assuming your character has senses and is experiencing the passage of time, this will happen immediately, at which point you will have to decide to take your declared action or not. There is no "reset, and wait until next instance of the trigger".
To pick a more normal example: if you say "When someone comes through the door, I shoot 'em", and then your buddy comes through the door followed by an orc a second later, you can shoot your buddy or not — but you can't ignore that trigger and then still have the action readied to shoot the orc.
Your plan is the same, except will go wrong immediately every time.
Or, in other words, there is not just sometimes a cost to readying an action, like the use of a spell slot or similar. There is always a cost — you use your action to ready for a circumstance, and if that situation doesn't happen or happens in a way you don't want to act on after all, you get nothing in exchange.
With your suggested trigger, immediately after your turn is over, you will perceive something, and therefore need to decide right then if you actually want to use your reaction to do the thing you planned. If you don't, the round moves on and you're done. This is equivalent to saying "I might shoot at the target. Yep, I do. That's my turn." or "I might shoot the target. Nope, wait, I decided not to. Skip my turn."