Mercedes c280 1995 during relanti momentarly, rpm fluctuate between 500 and 1000. is this normal?

Overdue by 61009 miles/kilometres. Give it some love and service it!!! Probably fuel pump or Automatic fluid low;

Check for vacume leak including intake. Spray some carb cleaner around intake and vacume hoses and listen for engine rpm to change.

Alignment has nothing to do with issue you report. It has to do with either ignition or fuel delivery.

Your car may have a cold start circuit/parts that need attention. Some even have a special injector for cold starts.

Hi,first of all I would get the battery and alternater checked to make shore they are bothe performing properly,I know you have replaced the battery but sometimes even new items can be forty,and with the fluctuation it maybe the maff sencer,the best thing is to have a diagnostic don to find the couse.
best of luck,PH.

fluctuation of rpm while running, if thats what u mean , then check the dtc, if P0174 or P0172 appear, find a vac. leak..

Transmission problem need to rebuild.

Depends on how long since all ignition components have been replaced, the O2 sensor and MAF.

Before you do all of that, have you had the egr recall done? There was a recall to repair the egr tubes on this year/model, not all vehicles had to get it done, to my knowledge, but you may call your local dealer with your VIN to see if your car qualifies for it. Symptoms are: rough idle, possible engine kill, slow acceleration, the feeling of a mis-fire, etc. I looked at replacing my MAF sensor but when the recall repair was made she purred like a kitten again.

your EGR valve is malfunctioning