I would reckon either:

- you have an active antenna (you are driving a VW or a car manufactured by a company associated with them) and the contact to the antenna power feed has gone duff (wiring or connector)

- you have a duff connection to the antenna, probably the signal lead

- one of the connectors in your wiring harness has some surface corrosion or some such that is screwing things up: pull all your connectors in the harness apart and re-seat them.