Sound and power button triggers by itself

This happened a few days ago, its a iphone 3G running 3.1.3 jailbreaked (2 months ago).
The ringer goes up by itself to maximum volume! randomly a few times a day.. Also, the "Slide to turn off" menu appears without me pressing the power button (if im playing a game or scrolling trough the menu it pops out of nowhere).

I tried a restore but it keeps happening..

Anyone experienced this?

 

nope no liquids on in... how do i check the sensors?

thanks!

edit: checked both headphone jack and lower dock connector port and none of them were red as it should be if water was in it ...