The canonical model for the formation of the Solar System involves the gravitational collapse of a nebula into (perhaps) several stars across several light years. Is it possible that two or more of the stars (or protostars) combined to form our Sun? Or would any stellar collision release so much energy that our Sun could not have formed the way we see it today? Have astronomers or astrophysicists created n-body orbital models that allow for a "soft" collision of two stars combined with the ejection of the other(s)?
The dynamics of the Solar System and the chemistry of the Solar System bodies don't support a hypothesis of a stellar merger later than formation of the protoplanetary disk which would have mixed-up things considerably and heavily disrupt any circumstellar disk. Thus this basically excludes any collision after the time one can start talking about a protostar, way before it even entered main sequence (as that's already the end of planetesimal formation).
Stellar mergers are certainly possible, but also relatively rare. Maybe protostars merging is a bit more common since they have less relative velocity.
However, unless the merger is straight it will typically deposit a lot of angular momentum. The sun seems to be a slow rotator for its spectral class. Hence it is not likely it was formed through a stellar merger.