I have a 5 ear old Frigidaire upright freezer. This past summer, my kids left it open before we went on vacation, as a result it iced over. I've defrosted it and it worked fine up until last week. Last week I noticed the high temp/open door alert on. I am not sure if my kids left the door open again, no icing over this time. I unplugged it for a day and plugged it again, it started running, and the freezies inside almost froze. It seems like the freezer will come on when it's unplugged and plugged in again, it'll run to a certain point and than it won't turn on again. The compressor is warm to touch and does not make strange noises. I've replaced the defrost thermostat, but it did not help.
I noticed that now unplugging and plugging it in does not always start it up. I sometimes have to play around with the temperature settings on the front control panel for it to come on. When it comes on, it seems to blow cold air, but the freezer door lacks the suction it once had.
Any ideas what to look at next?

I did a test last night, I unplugged the freezer and plugged it back in, it didn't start. I thank played around with the control panel, it turned on. It ran for a few hours, and stopped again. I slapped the door by the control panel and it turned on again. I did the same this morning and it turned on again.
I've ordered the control and display board.

The freezer is still running strong, I think it's fixed. denman, thank you for your help.