Can you tell me what it is called when your eyes cross by themselves?

Strabismus: There are many types of strabismus. Depending timing, duration, pattern, age, associated symptoms, strabismus might be a minor issue or a bigger issue. Good to get evaluated.

Convergence: Convergence is the active process of looking at something close to your nose. Sometimes a spasm occurs causing pain an double vision(spasm of near reflex). Esotropia is when one eye is misaligned inward causing double vision (congenital, developmental, acquired). Some people can develop a tendency to cross their eyes as they age, as in fatigue or illness, & hav distant double vis(decomp phoria