Samsung

its due to Software Force effect.. Update.. thats take it down for a restart suddenly.If after updated it again goes than it may be due Auto restart option.

Yes bro.. after all it has received 2 major OS Update. and now its already outdated . So thats why only.

no bro in every 2-3months only u will receive a Security patch update.. only..

bro alrrqdy One Ui 2.5 has ben released where werr u

bro till now the latest patch with one ui 2.5 has been released already for This device since a Month before... where r u .. that u r asking for patch update in One Ui 2.1