Annoying seat belt alarm glitch

2010 207 CTI

Apologies in advance if I get the terminology wrong - I'm not particularly technical!

My seat belt warning alarm keeps randomly going off, despite all the seat either being in use (with passengers) or plugged in (dog in the back seat). I'm assuming there's a relay between a weight sensor in the seat and the seat belt latch, and something's failed somewhere. It sometimes runs for the full two minutes and then cuts out, or constantly restarts, which is hugely annoying.

it seems to be random - sometimes it happens when it's just me in the car, at other times when there's only two of us.

I checked the fuse diagram on the offchance that there was a single fuse that ran it, but sadly the relevant fuse runs other useful things, so I can't just yank it out.

Is this a common issue, and is there anything else a relativel mechanical novice can try, or should I resign myself to a trip to the local garage?

TIA,

Trent