I have the same problem but my central locking stops working completely and this only happens on very cold days when it's cold enough for the windscreen to freeze over and the problem usually goes away after 20 mins of motorway driving with the heater all the way up, any suggestions would be much appreciated, checked the connectors under the glove compartment they are not loose, i have  also taken them all out and given them a good blast of electrical contact cleaner same with the connectors and relays under the bonnet and the binnacle itself as well but the problem still persists.

Just in case anybody else is having the same problem as me, it turned out to be a loose pin on one of the connections on the fuse board under the glove compartment, if i disconnect the on of the plugs running horizontally ( one nearest to the floor if that makes sense) which there is only two of it my problem goes away and has only resurfaced once since i figured it out and that was after 6 hours of driving on a motorway .