In v3 of Capital, Marx writes that “Capitalist production seeks continually to overcome [capitalism’s] immanent barriers, but overcomes them only by means which again place these barriers in its way and on a more formidable scale. The real barrier of capitalist production is capital itself.” (https://www.marxists.org/archive/marx/works/1894-c3/ch15.htm)
I’ve known people who think this process eventually points toward capitalism’s self-dissolution. That seems mistaken to me but I don’t know that I can establish that here, I just wanted to flesh out a partial thought that’s in the neighborhood. In saying capital is a barrier to capitalist production, I think the point is at least in part to identify some subjects (those engaged in capitalist production) who are going to be repeatedly smashed to pieces by colliding with an object (capital) -- lemmings hurling themselves off a cliff, crash test dummies in a car crashing into a wall. To put it another way, capitalist society periodically punches itself in the face at great length, mashing its features and cutting its knuckles. Many people are the cells and tissues, so to speak, in those specific locations on the body that endure laceration.
The specifically capitalist character of production compels the forward motion - the subject isn’t free - while that same character constitutes the barrier against which production collides and is destroyed in crises. It’s crucial, though, to bear in mind that while specific people get harmed, up to and including death (crisis is an element of capitalism’s tendency to social murder), partly in the form of destruction of specific capitals and specific productive units, capital per se, capitalist production per se, is not destroyed. Capital doesn’t punch itself in the face fatally, so to speak. Or to change the analogy, we can imagine Prometheus chained to a rock with his liver eaten regularly, the suffering never to end. That doesn’t capture the character of capitalism as a single process tied in knots, but it underlines that there’s no scenario where capitalism crisises itself to death.
There’s also a sense of subject/object inversion here, I think: capitalist production as subject encounters capital as object, and that encounter leaves the former bloody (well, leaves many people composing the actually existing practice of the former bloody, sometimes literally) and so in a sense the object becomes the subject - the barrier acts to limit and to destroy some producers, who become objects.
I said I’ve known people who think capital being capitalist production’s barrier will lead to capitalism ending. I’ve heard this sometimes said as ‘capital is its own limit’ (which is a fair way to put the point, as it’s not clear there’s a substantive difference between that phrasing and the bit of v3 I quoted above; I recall ‘capital is its own limit’ as Marx’s own phrase but can’t find it now), adding ‘and capital batters down all barriers.’ Hence capital will batter itself down. Marx seems to say this in the Grundrisse: capital “encounters barriers in its own nature, which will, at a certain stage of its development, allow it to be recognized as being itself the greatest barrier to this tendency, and hence will drive towards its own suspension.” (https://www.marxists.org/archive/marx/works/1857/grundrisse/ch08.htm)
I don’t recall the details anymore but I know Peter Thomas and Geert Reuten’s chapter in In Marx’s Laboratory (https://brill.com/display/title/17453) argues that Marx had one conception of crisis in the Grundrisse which he later abandoned, moving from crisis as secular to crisis as cyclical. I think one version of the former, the idea that capitalism will crisis itself to death, could be characterized as saying that capital as subject - propulsive forward motion driven by the imperative to turn money into more money - will eventually batter down capital as object. I think the opposite - capital as object will continually restrain capital as subject on pain of lacerating the latter intensely again and again, which is to say, on pain of literally destroying millions of lives (again, crisis as element of social murder). There’s no limit to capital’s capacity to self-limit, so to speak. (No amount of lemmings leaping off a cliff will harm the cliff.) The barrier can’t be overcome by capitalist production no matter the scale of catastrophe, unless literally of humanity dies - nearly everyone could be wiped out and in the aftermath still remain in social relations of market dependency, amounting to basically just resetting the clock of capitalism’s history for the same sorts of barbarity to replay in the future. None of which is to say capitalism can’t or won’t end - it can and I’m convinced it will - but rather that it won’t end itself, it’ll only be ended by a social revolution.