Can the molecule CH2(ONa)2 be stable? While studying about Cannizzaro reaction, it came to my mind as a wild thought what if this HCH(ONa)(ONa) molecule could pop out in some step of this reaction (not giving much details about how I thought it as it would be irrelevant). Then I thought this molecule might have some problem with stability. The $\mathrm{sp^3}$ hybridized carbon might have some have problem with spacing two -ONa groups close together.

So, is this molecule stable or not? If not why?
The species you are proposing would be a methanediol dianion (CH2O22–) with two sodium cations “attached” to it in some way, depending on the nature of the solvent.

While methanediol can indeed readily form an anion, with a pKa of 13.3, I find no mention of the dianion or any measure (or prediction) of the second pKa of methanediol.