DB reliability and delays

It's a risk I would not take. I would travel the evening prior and sleep near the airport.

Where is your flight from BER going?
It is probably as reliable as any route in Germany. The Sprinter makes limited stops.

This summer we have experienced more DB delays than ever before. I think your itinerary is too tight.

If flying out of Munich is not an option, would you consider flying from MUC to BER? Right now it looks like you can get a flight at the end of August for about 90 EUR, which is competitive with ICE fares.

Calculate back:

3 pm flight means
1 pm at BER airport means
12:15 pm from Berlin Südkreuz or Berlin Hbf (main station)

With a significant delay your plan would be on risk.

Tip: book train ticket through to BER airport, not only one of the two mentioned main stops in Berlin.

Any reason why you do not fly from MUC, Nuremberg or Memmingen?

Or you can fly from Munich to Berlin. Get there in an hour for around $90. It's a 4 hour train ride (at least). There's a flight every 2 hours.

DB has been horrible this year. It's a major problem, and political.

To have a reasonable chance to be to the airport no later than 1 PM ( assumes your destination is within the Schengen zone; otherwise you should be there by Noon) you need to be on a train by around 6 AM

Personally I would rather take a late train the night before than get up at 430

Or is it risky ?

Yes

Thank you all for your input. I looked at the DB schedule and this train "ICE 1008 to Berlin Hbf", starts from Munich at 5:50AM reach Berlin Südkreuz by 9:45AM. I thought in anyways I can be in Berlin by 10, so enough time to reach the airport. But overall looks like it is risky. Will make changes in my plan.

Smart move. I'm a firm believer in sleeping in - for as long as possible - on the day of my homebound flights. Getting up in Munich at 5 am would have made for a very long day.

With 2 hours time reserve I am more optimistic that it can work.

No major construction planned. Check DB construction portal if smaller things can be an issue.

If no major concern go for your original plan.

Even when DB's trains are running efficiently, there can still be occasional delays and cancellations. All sorts of things can happen, from work strikes to flooding to suicides... in an average year, a surprising 700 people manage to "end it all" right on Germany's railroad tracks (known as "Schienensuizid" in Germany.) Add to that number the unsuccessful suicides, which also result in the shutting down of railways for the same obvious reasons, including crime scene investigations. But it's not just about train delays. Travelers themselves sometimes fail to get to their assigned rail platforms on time for a variety of reasons. Stuff happens... Maybe rarely, but if it does just happen to happen on this very important day when you're heading home, on the tracks and at the time you have booked, the best way to ensure that your train ticket and your airline ticket will still be valid and useful is to arrive in your fly-out city on the day before.

Yesterday, Frankfurt airport -
https://www.dw.com/en/frankfurt-airport-climate-activists-stop-scores-of-flights/a-69760006

Due to an ongoing demonstration at the airport flights are currently suspended. Passengers are asked not to go to the airport for the time being.

DB cutting 30k workers due to lower long distance demand.
https://www.dw.com/en/german-rail-firm-deutsche-bahn-plunges-deeper-into-red/a-69762749

He cited weather events and dilapidated infrastructure, strikes, and accidents as reasons for the weaker demand and punctuality.