Have a 1998 Hitachi 50" Rear Proj TV and recently the picture has begun "jumping". It does this randomly, but is progressively getting worse. If I hit the side of the TV or shake it a bit (yes I know, don't hit things) the jumping will stop most of the time.

Anyone have an idea on what I might be able to do to fix the problem?

Being an older TV it may just be the CRT's (one or all of them) are starting to crap out on you. Could be convergence board malfunction. It may also just be a matter of a loose solder joint but either way the only way you will know what it is, is to get it looked at by a technician.

Being that old it may not be worth fixing it since parts will be harder to locate.

6 years old is too new to just trash but probably older than it is worth fixing.