Is my dog just wanting to play or aggressive

George has been getting aggressive again lately. It appears to me that when he is frustrated or excited he suddenly turns on me, bows down growling & barking and nips at my legs. As he escalates he then launches himself & snaps at my arms as I try to restrain him. I was just wondering if this was real aggression or him just wanting to get me to chase him & play. I have been grabbing him by his grab lead & locking him in the porch for 3-4 mins until he calms down which he does but he just keeps coming back for more. Most of the day he is fine but I just don't know how to stop him from doing it.
Any ideas?

Will he be distracted by a toy/ball? Have you turned your back on him?

If he's bowing down sounds like he wants to play...all be it in a too excited way. Don't grab him by the legs as this gives him physical attention. I would stand up, with my arms crossed and completely ignore him until he calms down....turning away sharply each time he jumps up. Once he has calmed down I would praise him gently.

I would also not get him so exited during playing and get him to stop and look at you every now and then while playing just to keep a check on how excited he's getting.

I'd agree with this tho' I am no dog behaviour expert.

Is he getting plenty of exercise?

I highly doubt it's aggression. If he really wanted to get you, he would have already.

I don't know George's history with you but it sounds a lot like Ivan did to me. Ivan would get so utterly overwhelmed that he would nip at me and make his way up to jumping up at my face snapping.

What is happening just before he behaves like this?

I think he is frustrated & wants to play or at least get rid of some energy but as he is reactive to other dogs I only take him out first thing in the morning & he does not play much even when I try. I throw balls & he may go once or twice but then he just ignores them.
I haven't been able to find anything that really gets him excited about play. It tends to happen when he is very excited or when he is bored. One example is I will throw two ball up & he will try to catch both running from one to the other but then if I am near he will turn on me and he does look & sound as if he means bussiness.

If he's not interested in playing with toys, have fun with him in other ways to burn off some energy. Does he like to swim? You could try carting, jogging, biking or nose work. Obedience and trick training helps a lot with mental stimulation.

The main problem I have is that he is fear aggressive with other dogs so other than one walk in the morning he does not get out of the garden due to the number of stray dogs here so I am limited to what I can do with him.

Are that's a problem. What about getting some agility equipment for your garden, or doing frisbee or ball play.

The other thing you could get is seem s nina Ottosson dog puzzles and do them with your dog. They really make their brain work and tires them out. Some imaginative shaping behaviour with clicker training would also give his brain a really good work out.

Oh and feeding him in imaginative ways like scattering kibble in the back garden and using kongs and buster cubes. Even a tennis ball with a small hole cut in it and kibble or treats out inside.