Ok, let's try this. Sometimes it works for me.
Break it down into small steps. Tell yourself all you have to do is stand up. Did it? Take sinute and feel good about accomplishing that!
Then tell yourself, all I have to do is walk into the bathroom where the shower is. If you can do that, another celebration! Each small step may give you just enough energy and motivation to take the next small step. If it doesn't, try again later. But give yourself some props for getting done any small step you could.
Like I said, this sometimes works for me--hope it works for you.
Sending good thoughts your way!