Some have it set to hibernate. Try SHUT DOWN next time.
If that fails, call it in as defective.
I just bought a HP dv 2550 special edition. I installed office, symantec antivirus and printer etc. softwares. The computer restarts automatically in about one minute after I shut it off. I updated the symantec antivirus and did a full system scan but had not found any virus in the computer. Can anybody tell me what is the problem with it? Thank you so much!