Basically it goes
1 good diet
2 multi vitamin
6 branch chain amino acids
This may not be exactly a 'jump start' but it gets me gains fast enough -- and they're sustainable -- hope this helps. I find these supps cheaper to buy (I get them from Costco) separate like this . . .
I am 49 (ex- competitive builder) who was out of the scene for about a year and a half. First I had to get my diet and lifting on track but that didn't take long as I have been around the block a few times, natural most of my life so I know my body very well.
Once I was satisfied with how things were going I too was looking for a little boost. Yah I'm 49 I could use one. I went to Drive and was very, very happy. I was able to push my strength up while the fat came off. Now I'm sitting at 258 at abround 17-18% body fat which for me is fairly healthy and my normal off season shape. Yah getting down for contest was always a *****.
Anyway worked well for me, supplied nice energy and mood enhancement as well.
Oh and at 38 you are no where's near old, I don't think age was much of a factor for me till I was past 45 and then I think it was more because I was out of shape. At 49 I still can out train most in the gym (almost all really), yah I hurt more but I have grown to kind of like it.