Why some analog clocks stop working after few seconds?

I have several very interesting chess clocks (two Solora, one Swiss Champion Looping) which have the same problem. One clock works perfectly, the other stops after few seconds. What is usually the problem? Thanks in advance for the answers!

Is it wound up?

Diagnosing mechanical problems in an old windup clock requires a visual inspection and patient and careful trial and error.

Like anything mechanical, they require periodic maintenance. In this case by a qualified technician i.e. a watchmaker. My bet is your clocks have never been serviced in their lives.if you don't know what to look for you aren't going to find anything.

Thanks guys. The problem is that a watchmaker is very expensive here in Switzerland.  Perhaps I can find someone who is retired and ask not so much for the work. 

 A paradox of kinds , guess it hard to find a good watchmaker these,s days ,

Welcome to the world of old mechanical things. Now imagine what it's like owning a vintage car.

Either there are dried gunk in the rolled up spring so it cannot fully unwind and/or the spring that you wind up is shifted so it touches one of the bars therfore it can not unwind.

I assume solora clockwork is complicated since it's small, on top of that it's aftersought so valuable. I wouldn't mess with it. If you're lucky only cleaning and lubricated is needed, that shouldn't cost that much.

thanks, I will once contact a specialist and see what he can do.

And thanks to everybody here, I was quite busy last time so I didn't have time to answer.

Have you tried looking for a "clockmaker" instead of a watchmaker? Working on mechanical/automatic wristwatches is a different skillset from clocks. If you value your chess clocks, unless you have basic knowledge of the internal workings of a mechanical clock, do not attempt any repair yourself. 

If and when you decide to bring them in for servicing/repair speak with the person who is doing the actual work to let them know that you value the chess clocks as collector items. Try and source original vintage parts. If this is not possible, and he has to use modern parts, tell him that you would like the old original parts returned to you as well. 

Also ask him what (if any) cleaning you wish to be done. Some watch/clockmakers think they are doing you a favor by cleaning the clock back to brand new condition. If you want the clock's appearance or vintage patina to remain unchanged tell him to only do necessary cleaning for the functionality of the clock. Good luck!

Maybe it's on a blitz setting?