ANSWER:

Prophet salla Allahu alaihi wa sallam has said that we must pray that we do not get sudden death. This doesn’t mean that whoever dies like this is sinful or that it is a bad sign. There were many righteous people who died all of a sudden. 

But once someone dies, the matter is in Allah’s hands and their fate is knowledge of the unseen. However, we must have good hope from Allah and pray for their forgiveness and elevation of ranks in Jannah.

my mother was all well she was lying on the bed busy with her mobile she got up from the bed and fell down n died she was all well I have heard if someone one died suddenly it so becouse of that person sin is it true…???