“Unstable energy” can’t be an uncaused cause. It is composed, but it cannot pre-exist itself to compose itself. It’s in motion (changing), and potential is reduced to act by another act. If a part of it moves itself, then that part is more fundamental the simply the “unstable energy”, so the “unstable energy” cannot itself be the first cause, but perhaps the part that actualized it is (if it can be determined to be non-composed, eternal, pure act, etc…). It is not pure act. It’s contingent (as in corruptible, that it may not be, for example, by undergoing a substantial change into something else), so at some point it could not be, and if it’s possible to not be, and so couldn’t be the necessary being by which all contingent beings have their existence at this moment. And more. Please review the cosmological arguments. It’s an apophatic analysis.