Thank you very much for the answers.

I actually went on a site that looks for hotel deals and found this pattern:

Hotel prices are high from now until about 3 weeks. Then there is a time period of about 2 weeks when the prices are really low (29 Feb onward) - many discounts in higher classed hotels.
After those two weeks - 5 weeks from now, the prices sky-rocket (Easter holidays could be a reason).
After that, prices go down, but only slightly. Far from those bargains in 3 weeks.

I compared around 10 hotels for 1 week periods.

One particular 5* hotel (New Otani) has a rate of 89€ in the week from 29 Feb. - 6 Mar.
The same hotel has a rate of 358€ in the week from 21 Mar. - 27 Mar.
And it has a rate of 154€ in the week from 11 Apr. - 17 Apr.

Incredible price differences, and I am not sure if it has got to do with some kind of high and low season or with the time period from now until those certain dates.
I thought maybe the best time to book the hotel is 3 weeks in advance, but maybe that is the wrong conclusion?

I just could not find an explanation why prices would be high from now until in 3 weeks, then go down for 2 weeks, and then go up again... (and I thought that might be the 'magic' time window when to book the hotel)