CLK seatbelt assister gone sluggish

[colh]

For the first 6 months or so with my '02 CLK, the seat belt assister would operate straight away on starting the engine. Just recently I always get a delay of a few seconds before the belt is offered. If (as I usually do) I have the wipers on auto then they do a single wipe - even with the car bone dry in the garage! - and immediately after, the seat belt comes out.
Anyway seen this or know how it gets into (and pref. out of) this state?
Thanks.

[colh]

Had to have new battery fitted the other day. Since then the problem has gone away, so I guess something somewhere needed a reset.