Are there any problems in serving a non-cooled (without cooling) a beer, as the doctor has told me not to take any cooled products. So I used to take beer once in couple of day without cooling it. The taste is different, but are there any real problems with consuming noncooled beers?
This article has very good information on how CO2 interacts with beer.
That being said, temperature plays a big part in the flavor of beer. Here is a the consensus of guidelines of what temperature types of beer and wine should be served.
There should be nothing wrong with refrigerating your beer and then warming it up. I really enjoy the flavor profiles in a lot of the darker, heavier beers I pour when they warm.
Just make sure that you clarify what temperature your fluids need to be before ingesting with your physician.
As with all alcoholic beverages there should be no issues drinking them cold, warm or even hot. The alcohol pretty much kills any nasty things. There may be some flavor issues. Flavors are more pronounced when the liquid is warmer as the volatile compounds that make up the flavors are more easily released but that is not necessarily a good thing in terms of flavor.
Should be just fine. Cooling or warming (in normal ranges) does not change the chemistry of beer.