It is pure coincidence, I’m afraid.
‘Suffix’ is a Latin word, and it can be split up into sub- ‘under, after’ and fixus, the passive perfect participle of figō ‘fix, fasten, stick to, bore through’. Literally, it just means ‘[something] stuck to the bottom/end (of …)’. Similarly, ‘prefix’ means ‘[something] stuck to the beginning (of …)’, ‘infix’ means ‘[something] stuck inside (of …)’, ‘adfix’ means ‘[something] stuck to (…)’, and ‘circumfix’ means ‘[something] stuck around (…)’.
Even a connection between Latin sub- and Hebrew sof is not likely, because Latin sub- is quite simply the non-transparent result of an earlier compound preposition exupo- ‘out from under’ (made up of ex- ‘from’ and upo- ‘under’) in very early pre-Italic. The preposition upo was lost as a standalone preposition and prefix very early on in Italic languages, but exupo survived and took its place. By aphaeresis, regular syncope, and semi-regular prefix lenition, *exupo- became *’ksupo- > *’supo- (aphaeresis), then *sup- (syncope), and finally *sub- (prefix lenition).
So in the case of ‘suffix’ specifically, the f comes from the verb meaning ‘fasten’ and is not connected to the prefix sub-; while in the case of sub- itself, the s comes from a different word than the ub.
Unless Hebrew sof ‘end’ happens to be a borrowing from an Italic language (which I think would be quite odd, considering that sub- only occasionally means ‘after’, its basic meaning being ‘under’—I do not know the etymology of sof, however), there really is no way that the two words can be related.