session by python to get data has a delay every few requests

Question

I use session by python to get data from some url,but after every few visits, there is a long delay.

My code is

import time

import requests


def main():
    session = requests.Session()
    start = time.time()
    for _ in range(100):
        _start = time.time()
        with session.get('https://www.mexc.ch/open/api/v2/market/depth', headers={
            "Cache-Control": "no-cache",
            "Pragma": "no-cache"
        }, params={
            "symbol": "BTC_USDT",
            "depth": "2"
        }) as res:
            print(time.time() - _start)
    end = time.time()
    print(f'time is：{end - start}')


if __name__ == '__main__':
    main()

and prints is

...
0.2015080451965332
0.20151209831237793
0.2026970386505127
1.340785026550293
0.2060239315032959
0.21337509155273438
0.2042250633239746
...

Output has a delay of more than 1 second.