Is it possible to do graduation again after getting low marks in the earlier degree exam?

Yes, the same can be done from your end. You need to write an application to the Principal of your college stating the reason for your reappearing for the said examination. You have to write down that you need improvement of your marks. The principal would forward the same to the Vice Chancellor of the University for the approval. Once you get the approval, fill up the application form available at the college counter along with the prevalent fees for the examination.
However, there is a point to be considered in this case. If your scorings in the next examination is less than the previous one, you may not get the benefits of the marks secured in the previous examination. If you gain marks as a result of next attempt, it would be your remarkable achievements.

There is no issue. You can do graduation again in the same subjects or in different subjects. You can do it from the same university or any other university also. You can do the graduation as a private candidate also. You can do the graduation in distance mode also.
You have mentioned that you did graduation but you have not mentioned what are the subjects you have studied and also you have not mentioned whether you did BA or B Sc or B.Com. Irrespective of that doing graduating again is not a problem.
I suggest you select a good university and apply for admission to a graduation course in distance mode. There are many universities offering graduation in distance mode and IGNOU is the best open university for doing graduation. You go ahead and apply for admission at the earliest.

As regards the issue of doing graduation again there is no problem as you can do it in the same subject or some other subject from the same college or other depending on your convenience.
One point which we have to keep in consideration in such a situation is that what are the gains you are going to achieve by doing that graduation degree again. Are you sure that you will be scoring more marks this time? Are you sure that you will be getting a job with that new degree with slightly enhanced marks? These are the crucial points which we have to take in consideration while taking a decision for going to attempt repeat of the degree course.
Alternatively, you can think of going for a skill based course which might be more useful for securing a job. For example a course in computer proficiency or digital marketing or some other niche area like that. So you can give a thought in that direction also.
Meanwhile if you are confident of your decision for going repeat graduation course then you can very well apply for it in the place of your choice choosing the subjects also of your choice.

There would not be any problem in repeating degree exam. I have seen many student who get low marks in academic exam applying for second time for getting good marks. So, you can apply for graduation again. There are various option for applying. You can apply again in same university or different university. Another best option is, you can apply through distance mode also. IGNOU is one of the best option for getting degree in distance mode. But, you didn't mention here in which discipline you want to complete your degree again. All subject are not offered in distance mode because of practical work.
As per career point of view, I would suggest that you should join job oriented course like digital marketing, web designing, cyber security course and another computer related course. If you are thinking just completing simple graduation then It's your wish. But, If you take up job oriented course then it would be more fruitful for future.