Sometimes complete lost of touch, what can it be?

Hello,

Sometimes I have a strange feeling in right side of by body especially hand that results in loosing touch of ball. I feel like if I completely lost my tennis skills.

I consider myself as quite a good player, if everything works fine I feel very confident on court.

But sometimes I loose my forehand and backhand and server, there is no problem with volleys, I have a feeling that hand is not mine, very difficult to describe. Then after few days it gets back to normal, sometimes it happens more often, sometimes less.

For the first time I noticed that when playing tennis.

I had a lot of medical tests with nothing found. Have you ever had something similar?

I can then notice that my hand also hurts and gets tired much faster when for example I user screwdriver.

Do you have any hints, what can I try, who ask for any advice here? Doctors say that everything is fine and indeed I can hold a pen and write, use computer mouse, hand is very string or at least as strong as left one, not problems at all, it is very subtle and I can feel the difference while using tennis racquet or playing table tennis.

It first happened like 15 years ago