It's always a bit hard to get back to work mode after vacation. Even for the kinds like me who love their jobs. At least normally the change of environment from home to office can ease this transition.
Now there isn't even that possibility as our fully remote work recommendations continue. While it's not strictly forbidden to go to the office, during this time of the year it's mostly empty anyway. Feels a bit pointless to visit the empty office just for the sake of getting that context switch done.
But visiting the office isn't everything there is when leaving to work. It's just the end of a set of tasks. There are other tasks to complete to get there, each one distancing you a bit from the home (and vacation) mode. Even when working from home regularly I had different routines for those mornings and leaving for office was just a few more steps on top of those.
If those regular steps aren't enough to get back to work mode you can always take a few extra steps to get there. All the way up to leaving out of the door and maybe walking around the block or sitting in your car for a moment before returning back home and start working.