Hey, everyone -- if you haven't noticed im new here.

Anyway a quick question:
I've been playing tennis recreationally on and off. Nothing serious. I've just gotten back into playing tennis again and changed my forehand grip to semi-western. I've been playing A LOT of tennis the past couple days for the first time in a couple years, about 5-6 hours a day.
And today, I noticed my hand starts to shake uncontrolably whenever I pick up anything remotely heavy (like a pitcher of juice, or a water bottle). That's never happened before. Also, my palm is really sore along with the inside of my fingers. My shoulder is a bit sore as well.
Is this normal because I haven't played in a while? Does this happen if you change grips, or a combination of both? I think it's because my fingers and hands aren't used to being in that position for long periods of time, but I just want to make sure.
Or am I holding the grip incorrectly?
Any help would be appreciated.