MacBook Pro doesn't boot sometimes, no startup chime, sleep light solid on

I have a macbook here, that seems to run just fine, only sometimes it won't boot at all. (Fans turn on, but screen stays black, no startup chime and the sleep light stays on)

Till now it always went back to booting normally again after a few startup attempts (and a bit of waiting)

Any ideas what could be the cause? If it happens as rarely as it does right now I wouldn't mind it too much, but is this perhaps the precursor to an impending death of the logic board? Or maybe something else?

Many Thanks