I have noticed this really weird bug several times;it always happen after a killing;I have noticed it after killing baal and after killing cows;the monster dies,then I take drops and the bug happens:the amount of gold increases in my stash for several seconds,not a lot of gold,just 10,20,30 gold each second;this bug has only happened a few times since I play diablo,so it is very rare (I wouldn't be surprised if you didn't know it);its' not a bad bug,but its' worth leting you know
Has anyone ever experienced it?

Are you playing in a party? Gold picked up by party members is shared among you all. So in a party of 8 players, if someone picks up 80 gold, you should see 10 gold added to your inventory.

gekko

Indeed,it happens in parties;so it is not a bug I guess

edited

Does this happen all the time, or do characters have to be in a certain area of each other for it to work?

It used to just be whoever was in the same area, including town. It could be really annoying when you were selling wands etc. for 25k gold and whoever was in town would get a piece of it. A lot of people would leave parties to sell stuff to avoid it. That was changed though some time ago, so I don't know the exact rules anymore for party loot.

This got removed from 1.08 to 1.09 due to (un)popular demand and bnet confusion.