Seizures in sleep?

My dog is 15 years old he has previously about 4 years ago had a tumor removed near the muscle of his right leg, the tumor was apparently one that didn't spread but I can not remember the name of it, I noticed about 3 months ago a lump on the same leg but it feels like its on the leg bone.

About 8 months ago we were woken by him yelping (I think) in his sleep, its hard to described but its like a yelp/cry. When I wake him he seems disorientated, it takes him a while probably about 5 minutes to sort of realise where he is. In the past 8 months he has had 7-8 attacks, as this is all I can call it.

4 of these attacks would have occurred in the last 7 1/2 months, however in the past 2 weeks he had 4 episodes this time 3 in one night and 1 on Wednesday night, I noticed the last four times he body like tenses up, one of the times when the 3 episodes occurred I was trying to wake him and his body when bending back and he neck was turning like it was going to bend right back on his spine then I was able to wake him from it. As I mentioned he takes a while to come round I put him down to see if he wanted the toilet or a drink the last two times but he just sits there and looks at me.

On Wednesday night I lay with him and rubbed his belly to ensure his body wasn't cramping if that's what it was, for the next 30 minutes he kept making a licking motion as if something was stuck in his throat or he was going to be sick. I rubbed under his neck and realised there was like a ball size lump in his throat which is not normally there and was not there the next morning.

Because he is so old and has bad legs and due to the tumor surgery, I made the choice I would let him live a happy life and not go through any more pain, he sleeps all but an hour a day and seems happy enough, he has started limping with the lump on his leg but my biggest concern is what is happening to him in his sleep. I don't want him to be in pain from this or if it is a seizure for him to not come out if one as himself. If you know what I mean.

I have him booked in for a consultation with the vet on Friday, but just thought I would get some insight if possible before the appointment in case I need to make a decision that is the best outcome for him as I do not want him to be in pain.

Thank you Dr Marie, Last night he was asleep and woke up there was no yelping noise in his sleep but he seemed disorientated and they seem to fall over, he got up and fell again and then made it is his bed and fell again. He has never done this and it was a bit concerning to see. I appreciate your advice you have given me. Keellie

Thank you Dr Marie, I appreciate all of your advice.