Vito 2015, with almost locked steering symptom at traveling straight

[KallOl]

This started some 2-3 weeks ago, or just before chrismas.
The symptom is that it gets "verry" difficult to change lanes with one hand on steering wheel. it is even hard with two hands, and suddenly when I have over powerd this lock it almost jumps in to next lane, it have been to exciting some times now, and I need to discuss possible symptom and solutions with someone.

Facts
It "locks" only when traveling straight or almost straight.
Not depending on speed.
Not empty of servo oil.
No funny noises.
250 000 Km
When overpowerd it stays easy to steer for a minutes or so, Im leaning towards worn ball joint, or perhaps top bearing in one of the strut towers?

Regards/ Newbie to this forum and car

 

[Smart320]

No idea what might be causing it, but if I owned it I would immediately take it off the road, sounds a danger to both yourself and anyone else . Get it fixed at once

 

[Jobsworth]

Sounds to me like it could be a seized uj on the steering column

 

[KallOl]

Something that came to my attention when I stopped at a gas station...and could not find the reservoir for servo fluid..do my car have electric power steering?!
I never had this new car before.

 

[KallOl]

Funny thing is when I took it to the shop an and described the symptom. No reaction from them when I told them the reservoir was full...
This was a MB dealer, and I booked a service.

 

[KallOl]

Update, Had it in to workshop today. And they changed lower steering column shaft, and some bolts on the steering rack that were a recall.
In my guessing I was right then, it was not the servo. and much cheaper. But car has run 240 000km now.