I share the OP's concern. I think the question here is one of the most important in physics. The idea of "frame" has to be abandoned or one is left with an eternity of infinite space and time sloshing about like a river or sea. It is becoming clear that things do not operate like that.
Einstein had the best stab at eliminating Newton's absolute space and time. Alas wrapping them up together and with the introduction of Minkowski space we are left with the problems of time in-variance, "rubber sheets" and still the need for some blackboard on which the fate of the universe is sketched.
For example if one considers that space and time are simply the effect of energy existing, and matter, then relativity can paint a slightly different picture. A bang in no space or time, even with infinite speed and energy, has a relative motion of zero. All directions are the same, so speed and acceleration are the same. Recent experiments have shown that at high temperatures quantum systems "lock" as degrees of freedom are limited and the system behaves as if extremely cold. Surely in the early Big Bang free from absolute space the degrees of freedom would be such that the event would be "cold" in the same way an aerosol spray freezes moisture out of the air? There is no observer or observer frame to be heated.