Main character finds one day spontaneously he can enter an accelerated state which renders him invisible. The people in fact the world around him appears frozen but is actually progressing at an infinitely slow pace. He can get his days work done and emerge to find only seconds or minutes have passed in the 'normal' world. Of course its a parable of relativity but nicely written, accessible and enlightening especially to the younger reader. He notices after doing this repeatedly he is ageing fast - this is about all I can remember of a short story I read maybe 35 or more years ago in Argosy (UK) magazine -can't remember the author, or even how it turned out.
Except for the part about being in Argosy this sounds a lot like "The Six Fingers of Time", a 1960 novelette by R. A. Lafferty which was also the answer to this question. First published in If, September 1960 (which is available at the Internet Archive), it is also available at Project Gutenberg.
The main character, Charles Vincent, tells the story to his doctor:
Vincent said, “It may not sound so silly if I tell it quickly. I awoke this morning to some very puzzling incidents. It seemed that time itself had stopped, or that the whole world had gone into super-slow motion. The water would neither flow nor boil, and fire would not heat food. The clocks, which I first believed had stopped, crept along at perhaps a minute an hour. The people I met in the streets appeared dead, frozen in lifelike attitudes. And it was only by watching them for a very long time that I perceived that they did indeed have motion. One car I saw creeping slower than the most backward snail, and a dead man at the wheel of it. I went to it, opened the door, and put on the brake. I realized after a time that the man was not dead. But he bent forward and broke his face on the steering wheel. It must have taken a full minute for his head to travel no more than ten inches, yet I was unable to prevent his hitting the wheel. I then did other bizarre things in a world that had died on its feet. I walked many miles through the city, and then I sat for hours in the park. I went to the office and let myself in. I accomplished work that must have taken me twenty hours. I then took a nap at my desk. When I awoke on the arrival of the others, it was six minutes to eight in the morning of the same day, today. Not two hours had passed from my rising, and time was back to normal. But the things that happened in that time that could never be compressed into two hours.”
He ages fast:
Dr. Mason made an entry in his private journal: “Charles Vincent, a completely authenticated case of premature aging, one of the most clear-cut in all gerontology. This man was known to me for years, and I here aver that as of one year ago he was of normal appearance and physical state, and that his chronology is also correct, I having also known his father. I examined the subject during the period of his illness, and there is no question at all of his identity, which has also been established for the record by fingerprinting and other means. I aver that Charles Vincent at the age of thirty is dead of old age, having the appearance and organic condition of a man of ninety.”