Solutions depending on where the build up is coming from:

Ground the underside of the pick guard or if its not shielded add some.
A common way is to fold a tab of copper attached to your extra ground wire at a place the pick guard makes contact. Or you could make a strip that fits under a pick guard screw.
Anti static spray on the pick guard.
Swap out the pick guard.
Wear different clothes or footwear.
Make sure you amps properly grounded and the socket at the wall is grounded.
Play somewhere else and see if it happens.
Run a humidifier.

Try this cheap alternative first,just rub your pickguard all over with a cling free dryer sheet,that often works.

Yeppers, seen this question posted on the Forum a few times. The dryer cling free sheet works great. I have a 89 EC Strat and I just keep one under the strings while the guitar is in the case. When I get it out to play, I just rub the guard a few times and she is good for the evening. Does seem a bit strange to have an nice signature guitar that yu have to use a dryer sheet on to play! Same with some of my Teles too. I live in a pretty dry climate so this happens here quite a bit.

Also I have heard of loosening the pickguard and actually putting on of these dry sheets underneath! Guy told me it works for months! And your guitar will smell great too!