why does my bass resonate when not being used.

[Flaked Beans]

but the fender jazz likes to play itself.
any ideas on how or why it does this?

The Elves. Those evil creatures are invisiable. Stay away from those little guys, please.

 

[rzero]

No guitar players are going to see this thread, right?

 

[Jeff Scott]

No guitar players are going to see this thread, right?

Wrong!

 

[Atshen]

Please, don't let Glenn Fricker see this thread.

 

[bucephylus]

i have 4 basses and one of them will resonate while in the stand,very annoying!
if i place it in the stand within minutes it starts to resonate and keeps getting louder as time goes on.
i forgot to turn off the amp one day and came home to the house shaking from the bass.lol
my other 3 basses can stay connected with no issues but the fender jazz likes to play itself.
any ideas on how or why it does this?

It’s called a feedback loop. That instrument happens to perhaps be a somewhat better receiver than your other basses, which could be a good thing. But, what is happening is a classic feedback loop. You can read all about it here.
Feedback - Wikipedia

 

[Franksvtartover]

Why anybody in TB even answer, someone that ignorant.

 

[bluesfordan]

I have a Gibson Les Paul and Marshall JCM 900 100 watt head going through 2 4x12 cabinets. I turn it up to full volume, set the gain all the way up, leave my Les Paul plugged in on the stand, then go to work. When I get home, I walk through the door to deafening feedback coming from the amp. My guitar seems to make sound when it's not being used. Should I take it in for repair?

the only solution is to run them over with heavy earth moving equipment, then burn the remnants. so sorry to have to tell you that.