Small issue. Not a biggie, just an annoyance.
I have 4, Dell T5810 workstations running W10, with indentical mobo & CPU. On 3 of them, FF starts in ~1 second. On the other, it takes ~ 10 seconds to start (and of course, it's the one I use most :)).
I've fussed with disabling all the add-ons...