determine the cause of huge packet delay

edit

Hi, I have some slow response on my web server. Fallowing the caputre, i noticed a 5s' gap after the server's first ACK to the client's http request, which to my understanding should be the first segment of the data transfer packet. I think a network congestion or tcp slow start, or an I/O interruption could've been the cause, but have no idea how to figure it out, could someone help to take a look at the capture and help about? Thanks in advance.

1   15:04:42.289164 172.180.202.64  172.180.131.29  TCP 60  53112 → 8080 [SYN] Seq=0 Win=28000 Len=0 MSS=1400 SACK_PERM=1 TSval=2071020872 TSecr=0 WS=128
2   15:04:42.289226 172.180.131.29  172.180.202.64  TCP 60  8080 → 53112 [SYN, ACK] Seq=0 Ack=1 Win=28960 Len=0 MSS=1460 SACK_PERM=1 TSval=2515609186 TSecr=2071020872 WS=128
3   15:04:42.289370 172.180.202.64  172.180.131.29  TCP 52  53112 → 8080 [ACK] Seq=1 Ack=1 Win=28032 Len=0 TSval=2071020872 TSecr=2515609186
4   15:04:42.289405 172.180.202.64  172.180.131.29  HTTP    2208    POST /mx_dspt/onlineServiceTmc?productId=680307&trace_id=30794 HTTP/1.1 
5   15:04:42.289436 172.180.131.29  172.180.202.64  TCP 52  8080 → 53112 [ACK] Seq=1 Ack=2157 Win=33280 Len=0 TSval=2515609186 TSecr=2071020872
6   15:04:47.552760 172.180.131.29  172.180.202.64  TCP 6992    8080 → 53112 [ACK] Seq=1 Ack=2157 Win=33280 Len=6940 TSval=2515614449 TSecr=2071020872 [TCP segment of a reassembled PDU]
7   15:04:47.552797 172.180.131.29  172.180.202.64  TCP 1304    8080 → 53112 [PSH, ACK] Seq=6941 Ack=2157 Win=33280 Len=1252 TSval=2515614449 TSecr=2071020872 [TCP segment of a reassembled PDU]