Even though you're account is six years old, you may not have hung out here before.

The sub title of "Ask Old People" can be a little misleading since many of the people resonding here are only 'old' by self-definition; using a descriptive adjective that has no specific meaning.

Many of those people, I believe, would probably rather chew off their tongue than to think forward to some of the harsher realities of being old ...versus the tweet machinations of pretending you're "old" because you're on Reddit and over 30.

But unfortunately, "solidly middle-aged" also means nothing in terms of your question and you've carefully avoided the terms 'dementia' and 'Alzheimer's' ... the terms have been gradually broadening as more is learned and finer gradations are able to be made through diagnosis.

Should I be worried or is this a natural part of aging?

Probably not (depending on your actual age and family history) and Yes.

But IANAD and the only real answers can only be determined by diagnostic testing.

"Senior moments" ARE a part of getting older, but one slip of the mind occasionally doesn't mean you have Alzheimer's ... extraordinary amounts of stress in your day to day life can have the same effect.

One troubling results of these sorts of slips (which our younger Selves wouldn't have been concerned about even for a moment) is that we begin to doubt ourselves... which become chronic stress.

No amount of factoids offered you here will tell you anything meaningful.

Go get tests run. The science is evloving but you can't do anything until you know the facts.