Screen is full of vertical coloured stripes and does not respond - iPhone 6

Hi

From time to time, the screen on my iPhone 6 stops working. The screen is filled with vertical coloured stripes, and I can only see the content on the screen briefly, sort of through the stripes. After that, it goes black. Nothing works on the screen or buttons, but if I get a message, the phone buzz. The connection to my Watch is also working, but the screen is greenish or black. It stays like that, I tried soft reset, multiple home button pushes... and every other thing I can think of. After a while it works again like normal... Lately this has happened every day, so I need to fix it!

Try full reset, and the error is still there. The phone is less than a year old, and has never been exposed to damp weather or moist, or fallen to the ground...

It first happened a few weeks after I connected my new Watch. Can that be a problem?

Anyone know what this is? And how to fix it?

ingeborg:)