I normally see them served hot so that's what I suggest, but I like them hot, cold, or room temp to be honest. My husband hates baked beans so it is a treat when I get them, and I will take them any way you are serving them.
I don't enjoy them, but I've never seen them served cold...wonder if I'd like them that way. The way my family serves them involves gob tons of bacon, I know that much, so they smell delicious while in the oven.
I've never heard of anyone voluntarily eating baked beans cold. I don't eat them because of all the sugar but I'll heat them up when serving. Now plain beans cold in a salad are fine.
Our son brings a crockpot full of his homemade bourbon and bacon baked beans for our family Christmas gathering. There is not a single bean in the pot when the meal is done. They are awesome!