So guys, I have a small update here:
Don't know if I can say my problem (Surface not waking up) is solved or not because not much time has passed to make a conclusion like that... but:
I don't have this issue any more!
After my surface not waking up twice a day for a few days I did not want to wait any more and tried to understand what the problem was. So I used the reliability log from windows to check for app-crashes. I realized that almost every day "microsoft.windowscommunicationsapps..." had crashed. And as far as I remembered every time my surface did not wake up there was this app/operation listed as "crashed". So I thought maybe that was the problem and tried to google it... found nothing... so further investigation was done:
I found out that my Surface had its last update on 12th of december. So far too long ago for microsoft updates. I tried to force my surface to update, but nothing would happen after showing me that there are updates available... So I went on and used the "recovery"-option from windows. The one where you keep all of your data, but all the windows files are checked for problems and are recovered.
Sadly I did not make any screenshots from the reliability-center
During the recovery session (68%) I got a bluescreen with the error "PAGE_FAULT_IN_NONPAGED_AREA". My Surface crashed on that bluescreen (bluescreen inception?

). I waited...waited...waited...but nothing happened. So I rebooted my Surface and it went just fine. My Surface updated all of my settings and downloaded all of my apps and everything looked just like before the recovery-session. I checked for updates and bam: a lot of them wanted to be installed. I did that...several times (update-installation-restart-update-installation-restart and so on). And since then I did not have the "not waking up"-Issue any more. The updates seem to work again. The reliability log shows only one time of microsoft.windowscommunicationsapps crashing. And that the day where I recovered windows. After that no apps or other operations crashed. But somehow I have "hardwareissues" showing up for almost every day (on the log...not on the screen or somewhere else...). All of them are an issue with the name "LiveKernelEvent". I did not have any crashes or anything like that...
So lets see what happens next... maybe you can use this information somehow...
Greetz