My computer restarts every night (between midnight and 8am)

[dalmations]

For the last 4-6 weeks my computer has been restarting by itself every night (12mid to 8am). I have checked the new software that was installed during this period but am unable to find any settings to restart. I am running Windows XP SP3 on an intel i3-4130 cpu at 3.4g with 8 gig ram and a Samsung SSD 120 gig. I also have two extra HDD's to store files and photos. I am also running Kaspersky anti virus. Can anyone help me with this anomaly? Thanks.

added 4/4/16: I forgot to add that I wish to keep my XP operating system. I feel that XP is sufficient for my needs as I am a senior.
Thank you for your suggestion.

I finally heard back from my anti virus support and they said their program is causing the problem and a fix will be forthcoming. Thank you for your help.

 

[LaborinjoRt]

Yes. Install windows 7, and it should reinstall everything back in place. I mean, you have more than enough strong PC to handle it