go to bed
To get into one's bed and sleep, ideally for eight hours. (Although one can nap in one's bed, the phrase "go to bed" is generally reserved for a longer period of sleep at the end of the day.) OK, I'm going to bed—good night, guys. Well, I'm not surprised you slept past noon if you went to bed at four in the morning! Mary usually tries to go to bed by 10 PM.
go to bed
(with someone) Go to go all the way (with someone).
go to bed
to go to where one's bed is, get into it, and go to sleep. It's time for me to go to bed. I want to go to bed, but there is too much work to do.