ONE of our ISP and Management of WAN(c2960) goes down. i need to know how do i investigate this issue.

[muhammadusama.shaukat]

ISP1 and ISP2 is connected to WAN (c2960). c2960 is in our network just to terminate ISPs on it. and 2 3 PCs are connected with it for testing.
WAN (c2960) is connected to Core (Nexus 5k)

yesterday an issue occur in our network. During which we were unable to access our WAN (c2960), meanwhile ISP2 completely goes down, while ISP1 was working somehow ok. also we were able to ping/access our PCs connected to WAN (c2960). only ISP2 and management of WAN switch was gone. so we reboot the WAN switch, but issue did not get resolve.
After half hour everything goes to normal.
our all switches are in separate management VLAN.
please help me and explain how do i find out what happened at that time.
did we observe some broadcast from ISP2?
I have checked the PRTG graphs of WAN (c2960), there was no any abnormal graph. i also checked the logs (show logging) on WAN switch but there was nothing.

please tell me what else information you need to know.
I will really appreciate everyone's help.
THANKS

[marce1000]

                   - Coordinate any resolving-efforts with the  malfunctioning-isp (provider) too

 M.

[muhammadusama.shaukat]

yes i have coordinated with the ISP. they are refusing anything. however i have coordinated with our sister company's IT person, as per him they also face some issue. we both have same ISP but our networks are totally different/isolated.

[Georg Pauwen]

Hello,

does the log (sh log) of the 2960 show anything ?

[muhammadusama.shaukat]

thanks for the reply.

no "show logging" did not display any log.

[MHM Cisco World]

do show version 

in output you can see what make router restart.
hope this help you.

[muhammadusama.shaukat]

dear i am not taking about any router. it is our switch cisco c2960.

[MHM Cisco World]

all have same filed.

router or SW