There's been some good debunking theories posted here that I absolutely think should be followed up on. However, most of them seem moot considering
that you've been living in that house for as long as you have. After several years, you just get to know your house and its idiosyncrasies.
The fact that the door is only gently closing itself- fully- at night, there has to be the question; anything new going on around the house and nearby
at night time?
I've also got a suggestion; if at all possible, install a soft night-light either inside or outside of your room near the door. At least that way
you're less likely to walk face-first into the door if it unexpectedly closes sometime during the night.
I keep night-lights around key points of
my house so I don't bump into things or fall down the stairs and kill myself when I need to get up during the night.
Now to possibly debunk some of the debunking, if only to rule things out and focus on other, more likely possibilities.
Seismic activity / geological changes seem like good ideas, but I'd question why nothing else in the house is being effected except that one door,
and only at night.
A new hole/crack in the roof or walls leads to the same question; why only at night?
Door hinges wearing down would, I think, be more gradual, not leading to a fully closed door every time right away.
Door / door frame / wall trauma seems possible, only you and your husband would know if that's happened recently.
Humidity / moisture issues, I'm a little more skeptical of, I'd think other things in the house would be effected, but has it been especially humid
this summer, more than normal?
Is your room on the top floor, is there an attic space above? Nocturnal critters roaming about at night seems a bit more plausible- though I'd wonder
why, after all this time, they'd only show up now.
New animal / insect damage to structure?
If all the 'normal' explanations have been ruled out, it sounds like it could be residual energy. The male voice and the muffled doorbell could be
evidence of this.
Objects, houses and land can get imprinted over the years. During traumatic events or things that happen habitually can happen again years later for
seemingly no reason. Echoes from the past. Sometimes it just gets triggered by something or another. Have any recent changes been made to the house or
near the house?
There's also another thing to try, even if you feel silly doing it, is to say (either out loud or 'aloud' in your mind), that 'you'd prefer to
have this door stay open, please. Could you stop closing it?' Can't hurt.