Hello and welcome to just answer
It sounds very much like you have either a motor fault or the wiper linkage is starting to sieze up. To diagnose this you will need to get to the wiper linkage and the wiper motor. Once you have access you can disconnect the linkage from the motor by disconnecting the ball joints. Once they have been disconnected you can then try to move each wiper arm in turn to see if it is stiff or moves freely. If either of them are stiff to turn then this is your problem. If they are both really free then it would point to a motor fault.
If it turns out to be the linkage going tight you can sometimes strip these down and clean up the spindles and then grease them and put it all back together as long as you can get them to move freely.
I hope that this helps and if I can help further please feel free to ask
do you no cost if took to garage for each possible repair ?
Hi to just look at it most garages would probably charge about an hours labour and upto 2 hours to remove and free the linkage up. It depends where abouts you live to how much the labour rate would be. A main dealer would charge a lot more than a independent garage so I would aim for somewhere around £45 to £55 per hour.
The parts would vary depending if you wanted new or secondhand and on Ebay they seem to vary from about £30 to just over £100.