be aware that your PC should be UNPLUGGED FROM THE MAINS at this point.
One fix might be to get the cog wheels (look in the open drawer to see if they are visible) lubricated , as after years they can wear or become sticky (my friend has had the same problem - he has to do this every 3 - 4 months) - and clean them with metholayted spirits He uses a cotton wool bud.
He then uses another clean bud soaked in WD 40 to re rub the cogs.... and he is jam free for a few months more.
(Or else it may need a trip to a computer service centre, )
I hope this may be of use to you.