I'm with you on this one olm; you are asking for advice, but just getting certain flippant comments.
I have had this happen to me with several Omegas; switches become sticky over time. I have had it on the door window buttons, the door mirror controls, and the remote boot release button. The coating on the door handle surround where the window switches are located also loses its coating. It isn't, as has been suggested, dirt or sticky fingers, but the plastic rubbery coating breaking down. I have tried all types of cleaner on them with no improvements. When it last happened on the boot release button, cleaning had no effect, and the boot symbol ended up coming off the switch with the various cleaners used (including various upholstery / fabric cleaners), and the only solution was to buy a brand new switch as most in beakers yards have suffered the same fate.
The only partial success I have had is with the door handle surround. With careful scraping, the plastic coating comes off and leaves a hard plastic shiny finish underneath. I've had better results doing this with the light grey trim, rather than the black.
Helpful responses are what most OOfers want, not belittling comments.