Phone gets stuck after charging My phone is somewhat older sony xperia v. still running on android v4.1 jelly bean.
recently it behaves abnormaly. whenever I put it in charge (wall adapter or usb plugged into a laptop) , it only sometimes very slow to respond while chargin and almost always slow to respond after i remove the charging cable. its usually working very much fine but in only these situations it acts abnormly. 

i don't have many apps installed and i usualy force-stop them after i use them. and also phone works very much fine in normal situations. only after charging this happens.

why is this happening and what can i do to avoid this? please help
Your device is very old and contains dozens of vulnerabilities. Therefore one very likely scenario is that malware has infected your system using one of the vulnerabilities and now uses your CPU to do something, e.g. Bitcoin mining or something similar.

As on Smartphones heavy CPU usage results in high battery usage (which is usually easy detectable by the user) this malware only abuses your device while it is charging.

As it is so old I assume it has only one CPU core and if the malware is active the CPU operates at full capacity and hence the device is nearly blocked.
The detection if the device is charging or not is a bit slow therefore this effect continues some time after you have disconnected the phone from the charger.