Default [Q] Nexus 5 (boot?) loop

my Nexus does't start anymore (see videos)

I had a SlimKat Stable for a few weeks installed (should be 4.4.2 or 4.4.4 ?)
It came with an update message a few weeks ago i downloaded it but did not flash it.

Few weeks ago nexus did just turn off and now nothing.

I do not press anything it does that when its plugged in.
Doesn't respont if it's not